Bootstrap server service, fixes to server state management

* Added bootstrap service call to do DBMS side bootstrap operations
  during the cluster bootstrap.
* Added last_committed_gtid() to provider interface
* Implemented wait_for_gtid() provider call
* Pass initial position to the server state

dbsim/db_server_state.hpp

@@ -31,6 +31,7 @@ namespace db
                 server_id,
                 address,
                 working_dir,
+                wsrep::gtid::undefined(),
                 1,
                 wsrep::server_state::rm_async)
             , mutex_()