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)
(cherry picked from commit 55997a627ecf155499621b17eb7e118787536765)