Correct msftidy disclosure date check

This correct msftidy's disclosure date check to do the following:

1. If the module has a disclosure date, the check should kick in.
2. If the module is an exploit, and doesn't have a disclosure
   date, then it will be flagged.
3. If the module is an auxiliary, and doesn't have a disclosure
   date, then it will NOT be flgged (because not all aux modules
   target bugs/vulns like exploits do).
Land #3198, msftidy disclosure date fix