(PUP-847) Group has no default

From http://msdn.microsoft.com/en-us/library/windows/desktop/ms676927(v=vs.85).aspx
it has been noted that there really isn't a default group on Windows, so trying
to specify this could lead to issues of sync. 

If someone has not specified a group, then we shouldn't try to manage it. 
This commit changes the behavior to allow group to stay as it is unless 
explicitly managed.