MXS-2011 Use alternative servers

If the replication fails using the current config, we retry
immediately using another config, without waiting anything at
all.

Only when we have unsuccessfully tried with all servers, will
we wait a while before starting again.

server/modules/routing/binlogrouter/blr.cc

@@ -817,6 +817,7 @@ static MXS_ROUTER* createInstance(SERVICE *service, MXS_CONFIG_PARAMETER* params
      * automatic master replication start phase
      */
 
+    inst->current_config = 0;
     rc = blr_file_read_master_config(inst);
 
     /*