Fixed a bug in propagation of PUBLISH via the cluster bus.

This bug was spotted by clang on FreeBSD.

src/cluster.c

@@ -902,7 +902,7 @@ void clusterSendPublish(clusterLink *link, robj *channel, robj *message) {
     } else {
         payload = zmalloc(totlen);
         hdr = (clusterMsg*) payload;
-        memcpy(payload,hdr,sizeof(hdr));
+        memcpy(payload,hdr,sizeof(*hdr));
     }
     memcpy(hdr->data.publish.msg.bulk_data,channel->ptr,sdslen(channel->ptr));
     memcpy(hdr->data.publish.msg.bulk_data+sdslen(channel->ptr),