Use normalize_uri for module wp_property_upload_exec 

Older http/webapp exploits do not use the "normalize_uri" function, causing bad URIs to be generated that some servers don't like. For instance after installing wp_property in metasploitable2 the URI used doesn't have a leading / causing errors:

```
192.168.8.1 - - [27/Mar/2014:07:23:36 -0400] "GET wordpress/wp-content/plugins/wp-property/third-party/uploadify/mYfXH.php HTTP/1.1" 400 310 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)"
```

Validation
-------------

```
msf exploit(wp_property_upload_exec) > rexploit
[*] Reloading module...

[*] 192.168.8.150:80 - Uploading payload AqAyX.php
[*] Started bind handler
[*] 192.168.8.150:80 - Executing payload AqAyX.php
[*] Sending stage (39848 bytes) to 192.168.8.150
[*] Meterpreter session 1 opened (192.168.8.1:60291 -> 192.168.8.150:4444) at 2014-03-27 05:21:31 -0700

^C[-] Exploit failed: Interrupt 

meterpreter > getuid
Server username: www-data (33)
meterpreter > pwd
/var/www/wordpress/wp-content/plugins/wp-property/third-party/uploadify
meterpreter > sysinfo
Computer    : metasploitable
OS          : Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686
Meterpreter : php/php
meterpreter > meterpreter > 
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.8.150 - Meterpreter session 1 closed.  Reason: User exit
msf exploit(wp_property_upload_exec) > exit
```

Other Instances
--------------------

A quick grep found many other similar instances but since I don't have all the apps to test I didn't touch them:

```
$ grep -r "if uri\[-1,1\] != '/'" *
linux/http/dolibarr_cmd_exec.rb:    uri << '/' if uri[-1,1] != '/'
linux/http/symantec_web_gateway_exec.rb:    uri << '/' if uri[-1,1] != '/'
linux/http/symantec_web_gateway_file_upload.rb:    uri << '/' if uri[-1,1] != '/'
linux/http/vcms_upload.rb:    uri << '/' if uri[-1,1] != '/'
linux/http/webid_converter.rb:    uri << '/' if uri[-1,1] != '/'
linux/http/webid_converter.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/ajaxplorer_checkinstall_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/apprain_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/auxilium_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/mobilecartly_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/mobilecartly_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/phpldapadmin_query_engine.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/phpscheduleit_start_date.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/phpscheduleit_start_date.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/phptax_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/qdpm_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/qdpm_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/sflog_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/sflog_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/sun_jsws_dav_options.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/webpagetest_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
multi/http/webpagetest_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/egallery_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/joomla_tinybrowser.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/narcissus_backend_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/php_wordpress_foxypress.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/projectpier_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/projectpier_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_advanced_custom_fields_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_advanced_custom_fields_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_advanced_custom_fields_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_advanced_custom_fields_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_asset_manager_upload_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_google_document_embedder_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/wp_google_document_embedder_exec.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/xoda_file_upload.rb:    uri << '/' if uri[-1,1] != '/'
unix/webapp/xoda_file_upload.rb:    uri << '/' if uri[-1,1] != '/'
windows/http/hp_sitescope_runomagentcommand.rb:    uri << '/' if uri[-1,1] != '/'
```