Make all WATCHers dirty when the slave reloads the DB.

src/replication.c

@@ -427,6 +427,7 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
             return;
         }
         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Loading DB in memory");
+        signalFlushedDb(-1);
         emptyDb();
         /* Before loading the DB into memory we need to delete the readable
          * handler, otherwise it will get called recursively since