In uipc_close(), we no longer always free the unpcb, as the last reference

may be dropped later.  In this case, always unlock the unpcb so as not to
leak the lock.

Found by:	kris (BugMagnet)

sys/kern/uipc_usrreq.c

@@ -593,7 +593,8 @@ uipc_detach(struct socket *so)
 	if (freeunp) {
 		UNP_PCB_LOCK_DESTROY(unp);
 		uma_zfree(unp_zone, unp);
-	}
+	} else
+		UNP_PCB_UNLOCK(unp);
 	if (vp) {
 		int vfslocked;