Remove some redundant code

Function nodeIp2String in cluster.c is exactly
anetPeerToString with a pre-extracted fd.

src/cluster.c

@@ -1034,22 +1034,9 @@ void clusterProcessGossipSection(clusterMsg *hdr, clusterLink *link) {
 
 /* IP -> string conversion. 'buf' is supposed to at least be 46 bytes. */
 void nodeIp2String(char *buf, clusterLink *link) {
-    struct sockaddr_storage sa;
-    socklen_t salen = sizeof(sa);
-
-    if (getpeername(link->fd, (struct sockaddr*) &sa, &salen) == -1)
-        redisPanic("getpeername() failed.");
-
-    if (sa.ss_family == AF_INET) {
-        struct sockaddr_in *s = (struct sockaddr_in *)&sa;
-        inet_ntop(AF_INET,(void*)&(s->sin_addr),buf,REDIS_CLUSTER_IPLEN);
-    } else {
-        struct sockaddr_in6 *s = (struct sockaddr_in6 *)&sa;
-        inet_ntop(AF_INET6,(void*)&(s->sin6_addr),buf,REDIS_CLUSTER_IPLEN);
-    }
+    anetPeerToString(link->fd, buf, REDIS_CLUSTER_IPLEN, NULL);
 }
 
-
 /* Update the node address to the IP address that can be extracted
  * from link->fd, and at the specified port.
  * Also disconnect the node link so that we'll connect again to the new