simplify robust mutex unlock code path

right now it's questionable whether this change is an improvement or
not, but if we later want to support priority inheritance mutexes, it
will be important to have the code paths unified like this to avoid
major code duplication.

src/thread/pthread_mutex_unlock.c

@@ -5,6 +5,7 @@ int pthread_mutex_unlock(pthread_mutex_t *m)
 	pthread_t self;
 	int waiters = m->_m_waiters;
 	int cont;
+	int robust = 0;
 
 	if (m->_m_type != PTHREAD_MUTEX_NORMAL) {
 		if (!m->_m_lock)
@@ -15,16 +16,15 @@ int pthread_mutex_unlock(pthread_mutex_t *m)
 		if ((m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE && m->_m_count)
 			return m->_m_count--, 0;
 		if (m->_m_type >= 4) {
+			robust = 1;
 			self->robust_list.pending = &m->_m_next;
 			*(void **)m->_m_prev = m->_m_next;
 			if (m->_m_next) ((void **)m->_m_next)[-1] = m->_m_prev;
-			cont = a_swap(&m->_m_lock, 0);
-			self->robust_list.pending = 0;
-			goto wake;
 		}
 	}
 	cont = a_swap(&m->_m_lock, 0);
-wake:
+	if (robust)
+		self->robust_list.pending = 0;
 	if (waiters || cont<0)
 		__wake(&m->_m_lock, 1, 0);
 	return 0;