Fixes to streaming rollback

* Check fragment removal error code in prepare phase. It is possible
  that the transaction gets BF aborted during fragment removal.
* Mark fragment certified in certify_fragment() even if the provider
  returns cert failed error. With current wsrep-API error codes
  it may not be possible to distinquish certification failure
  and BF abort during fragment replication. This may also be a
  provider bug. As a result rollback fragment may sometimes be
  replicated when it would not be necessary.

src/client_state.cpp

@@ -67,6 +67,7 @@ int wsrep::client_state::before_command()
 {
     wsrep::unique_lock<wsrep::mutex> lock(mutex_);
     debug_log_state("before_command: enter");
+    store_globals(); // Marks the control for this thread
     assert(state_ == s_idle);
     if (transaction_.active() &&
         server_state_.rollback_mode() == wsrep::server_state::rm_sync)