logwatcher: gc superfluous broadcasts on watcher_cond

the logwatcher has now been, for a long time, the only thread
waiting on it

src/fellow_log.c

@@ -5710,7 +5710,6 @@ fellow_logwatcher_thread(void *priv)
 			ffd->watcher_state = FLW_S_FLUSHING;
 			fellow_logwatcher_flush(ffd, 0);
 			ffd->watcher_state = FLW_S_REWRITING;
-			AZ(pthread_cond_broadcast(&ffd->watcher_cond));
 			AZ(pthread_mutex_unlock(&ffd->logmtx));
 			if (new_log_fdr.size ||
 			    fellow_logwatcher_need(ffd, NULL) == need)
@@ -5731,7 +5730,6 @@ fellow_logwatcher_thread(void *priv)
 		ts.tv_sec += dts.tv_sec + ts.tv_nsec / NSEC;
 		ts.tv_nsec %= NSEC;
 		ffd->watcher_state = FLW_S_WAITING;
-		AZ(pthread_cond_broadcast(&ffd->watcher_cond));
 		i = pthread_cond_timedwait(&ffd->watcher_cond, &ffd->logmtx,
 		    &ts);
 		assert(i == 0 || i == ETIMEDOUT);