Fix write() errno error

src/cluster.c

@@ -2120,7 +2120,7 @@ void clusterWriteHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
     nwritten = write(fd, link->sndbuf, sdslen(link->sndbuf));
     if (nwritten <= 0) {
         serverLog(LL_DEBUG,"I/O error writing to node link: %s",
-            strerror(errno));
+            (nwritten == -1) ? strerror(errno) : "short write");
         handleLinkIOError(link);
         return;
     }