Coverity defects
    
    History:
    The commit b9eeb2e1a8e688dfec753e8965d0e5aeb119e638 for Ticket #481
    "expand nested posix groups" introduced 4 coverity defects.  Commit for
    the fixing patch e9941a2915ac848abe9a4afe802d0432aa0c354a failed to solve
    13102: Resource leak.
    
    Fix Description: This patch explicitly calls slapi_valueset_free for
    the leak reported object muid_old_vs.
    (cherry picked from commit 544f027193139a109aeb14145ae1d77c4bdcc618)