[useradmin] Fix stops importing users silently if objectClass posixGroup exists in group

Attempting add/sync group will not add users if the objectlass posixGroup exists in the group LDAP entry.  This happens silently so it was very hard to detect.

In HUE-1767, we introduced logic to prevent the addition of "members" if the posixGroup objectClass.

This causes problems if a customer has a "mixed use" group that has both non-posix and posix members.

 

This problem occurs in ldap_access.py in function _transform_find_group_results.