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)

ldap/servers/plugins/posix-winsync/posix-group-func.c

@@ -497,6 +497,7 @@ propogateMembershipUpward(Slapi_Entry *entry, Slapi_ValueSet *muid_vs, int depth
                     slapi_valueset_add_value(muid_upward_vs, v);
                 }
             }
+            slapi_valueset_free(muid_old_vs);
         }
 
         /* Update this group's membership */