Fix and improve reliability in CVE-2010-2343

Hi @sgabe,

This pull request tries to clean and improve reliability on https://github.com/rapid7/metasploit-framework/pull/2970

* Fixing the ESP before executing the decoder to avoid crashes.
* Spraying the stack with rop nop's so the exploit works in XP SP3 and windows 7 SP1 opening the file with Add Playlist or Drag & Drop. Otherwise the exploit only work on XP SP3 when opening the file with "Add Playlist".

Feel free to review and check, and land into your repository once you feel comfortable so https://github.com/rapid7/metasploit-framework/pull/2970 will be automatically updated and ready to go! Thanks!