metasploit check is smarter

If MetasploitAPI fails to load the set working_msf_api to False
otherwise assign MetasploitAPI to msf_api. This allows users who do not
want to install msgpack the ability to use Kvasir to import scans.
metasploit import cleanup
Merge pull request #22 from grutz/msfapi_load

MetasploitAPI cleanup in skaldship and controllers