better error handling for NBO failures

when losing error voting:
- if NBO has failed locally (DBMS side), don't override original DBMS
  error so it gets reported to the client
- otherwise, report "query interrupted" instead of "error during commit"

include/wsrep/client_state.hpp

@@ -790,10 +790,12 @@ namespace wsrep
          * passed to begin_nbo_phase_one().
          *
          * @param keys Key array.
+         * @param has_error True if client thread has errored.
          * @param wait_until Time point to wait until for entering TOI for
          *                   phase two.
          */
         int begin_nbo_phase_two(const wsrep::key_array& keys,
+                                bool has_error,
                                 std::chrono::time_point<wsrep::clock>
                                 wait_until =
                                 std::chrono::time_point<wsrep::clock>());