SR Rollback handling fixes

* Handle BF rollback also in after_statement() call.
* Added missing after_apply() call when handling rollback fragment.
* Fixed state changes when rollback is starated during preparing state.

src/server_state.cpp

@@ -98,6 +98,7 @@ namespace
 
         high_priority_service.remove_fragments(ws_meta);
         high_priority_service.commit(ws_handle, ws_meta);
+        high_priority_service.after_apply();
         return ret;
     }