Fix double MOVED reply on unblock at failover (#2734)

#2329 intoduced a bug that causes a blocked client in cluster mode to
receive two MOVED redirects instead of one. This was not seen in tests,
except in the reply schema validator.

The fix makes sure the client's pending command is cleared after sending
the MOVED redirect, to prevent if from being reprocessed.

Fixes #2676.

---------

Signed-off-by: Viktor Söderqvist <[email protected]>

Author: zuiderkwast

src/blocked.c

@@ -340,7 +340,7 @@ void disconnectOrRedirectAllBlockedClients(void) {
 
             if (server.cluster_enabled) {
                 if (clusterRedirectBlockedClientIfNeeded(c))
-                    unblockClient(c, 1);
+                    unblockClientOnError(c, NULL);
             } else {
                 /* if the client is read-only and blocked by a read command, we do not unblock it */
                 if (c->flag.readonly && !(c->lastcmd->flags & CMD_WRITE)) continue;