MXS-1266: files are saved in GTID repo at creation time

Files are saved in GTID repo at creation time: this allows to show
files without transactions via SHOW [FULL] BINARY LOGS

The FULL keywords add domain_id and server id to the output as file
prefix: 0/10122/mysql-bin.000080

server/modules/routing/binlogrouter/blr_master.c

@@ -1103,6 +1103,7 @@ blr_handle_binlog_record(ROUTER_INSTANCE *router, GWBUF *pkt)
                             strcpy(router->pending_transaction.gtid, mariadb_gtid);
                             /* Save the pending GTID components */
                             router->pending_transaction.gtid_elms.domain_id = domainid;
+                            /* This is the master id, no override */
                             router->pending_transaction.gtid_elms.server_id = hdr.serverid;
                             router->pending_transaction.gtid_elms.seq_no = n_sequence;
                         }
@@ -2274,6 +2275,12 @@ static void blr_register_heartbeat(ROUTER_INSTANCE *router, GWBUF *buf)
                                 "serverid",
                                 buf);
 
+    /**
+     * Keep the original master server id
+     * for any further reference.
+     */
+    router->orig_masterid = atoi(val);
+
     /**
      * Set router->masterid from master server-id
      * if it's not set by the config option