MDEV-21025 Server crashes on START TRANSACTION after INSERT IGNORE (#1489)

If a transaction had no effect due to INSERT IGNORE and a new
transaction was started with START TRANSACTION without committing
the previous one, the server crashed on assertion when starting
a new wsrep transaction.

As a fix, refined the condition to do wsrep_commit_empty() at the end
of the ha_commit_trans().

mysql-test/suite/galera/r/mdev_21025.result

+connection node_2;
+connection node_1;
+CREATE TABLE t1 (f1 INTEGER PRIMARY KEY);
+START TRANSACTION;
+INSERT INTO t1 (f1) VALUES (1);
+START TRANSACTION;
+INSERT IGNORE INTO t1 (f1) VALUES (1);
+Warnings:
+Warning	1062	Duplicate entry '1' for key 'PRIMARY'
+START TRANSACTION;
+DROP TABLE t1;

mysql-test/suite/galera/t/mdev_21025.test

+#
+# MDEV-21205
+#
+# Start transaction after INSERT IGNORE which had no effect and
+# kept the transaction open caused an assertion on the following
+# START TRANSACTION because the empty transaction was not properly
+# terminated.
+#
+
+--source include/galera_cluster.inc
+CREATE TABLE t1 (f1 INTEGER PRIMARY KEY);
+START TRANSACTION;
+INSERT INTO t1 (f1) VALUES (1);
+
+START TRANSACTION;
+# This INSERT succeeds with duplicate key warning due to IGNORE clause
+# and keeps the transaction open. The following START TRANSACTION causes
+# an assertion if the bug is present.
+INSERT IGNORE INTO t1 (f1) VALUES (1);
+START TRANSACTION;
+
+DROP TABLE t1;

sql/handler.cc

@@ -1705,7 +1705,8 @@ int ha_commit_trans(THD *thd, bool all)
     thd->mdl_context.release_lock(mdl_request.ticket);
   }
 #ifdef WITH_WSREP
-  if (wsrep_is_active(thd) && is_real_trans && !error && (rw_ha_count == 0) &&
+  if (wsrep_is_active(thd) && is_real_trans && !error &&
+      (rw_ha_count == 0 || all) &&
       wsrep_not_committed(thd))
   {
     wsrep_commit_empty(thd, all);