TODO: Improve self.searchedGroups

[adeutscher]

When going over the code, I realized that there were a lot of return statements in getGroupMembers that didn't check for depth and clear self.searchedGroups before returning the result.

Instead of tracking all of these possible exit points, I should put a single clearing self.searchGroups at the top of the getGroupMembers and any other method that uses self.searchedGroups.

In addition, each cache-using call should use a unique cache, in case a cache-using method calls another cache-using method.

[adeutscher]

Additional note: self.searchedGroups should only be populated by DNs.

[adeutscher]

Already somewhat implemented in past commits as flushCaches(). Still need to make sure that it's covered in all the necessary places.

[adeutscher]

Expanding the scope of this ticket. Just in case one cache-using item calls another cache-using item that uses a clean slate. Updating description.

[adeutscher]

Adjusted caching system. Different calls of recursive functions such as getGroupMembers() (i.e. getting the members of two different groups) will use separate caches.

Tested against Active Directory:389, Active Directory:3268, and FreeIPA.