Cluster: fix memory leak of cached master.

This is what happened:

1. Instance starts, is a slave in the cluster configuration, but
actually server.masterhost is not set, so technically the instance
is acting like a master.

2. loadDataFromDisk() calls replicationCacheMasterUsingMyself() even if
the instance is a master, in the case it is logically a slave and the
cluster is enabled. So now we have a cached master even if the instance
is practically configured as a master (from the POV of
server.masterhost value and so forth).

3. clusterCron() sees that the instance requires to replicate from its
master, because logically it is a slave, so it calls
replicationSetMaster() that will in turn call
replicationCacheMasterUsingMyself(): before this commit, this call would
overwrite the old cached master, creating a memory leak.

2 files changed, 9 insertions, 4 deletions

diff --git a/src/replication.c b/src/replication.c
index f8951ad14..a5e94db7a 100644
--- a/src/replication.c
+++ b/src/replication.c
@@ -1996,7 +1996,10 @@ void replicationSetMaster(char *ip, int port) {
     cancelReplicationHandshake();
     /* Before destroying our master state, create a cached master using
      * our own parameters, to later PSYNC with the new master. */
-    if (was_master) replicationCacheMasterUsingMyself();
+    if (was_master) {
+        replicationDiscardCachedMaster();
+        replicationCacheMasterUsingMyself();
+    }
     server.repl_state = REPL_STATE_CONNECT;
 }
 
diff --git a/src/server.c b/src/server.c
index f7fb4f882..6aeb5aa9a 100644
--- a/src/server.c
+++ b/src/server.c
@@ -3886,12 +3886,14 @@ void loadDataFromDisk(void) {
                 (float)(ustime()-start)/1000000);
 
             /* Restore the replication ID / offset from the RDB file. */
-            if ((server.masterhost || (server.cluster_enabled && nodeIsSlave(server.cluster->myself)))&&
+            if ((server.masterhost ||
+                (server.cluster_enabled &&
+                nodeIsSlave(server.cluster->myself))) &&
                 rsi.repl_id_is_set &&
                 rsi.repl_offset != -1 &&
                 /* Note that older implementations may save a repl_stream_db
-                 * of -1 inside the RDB file in a wrong way, see more information
-                 * in function rdbPopulateSaveInfo. */
+                 * of -1 inside the RDB file in a wrong way, see more
+                 * information in function rdbPopulateSaveInfo. */
                 rsi.repl_stream_db != -1)
             {
                 memcpy(server.replid,rsi.repl_id,sizeof(server.replid));