MDEV-16929 Assertion ... in close_thread_tables upon killing connection

Problem was that the code didn't handle a transaction created in innodb
as part of a failed mysql_lock_tables()

mysql-test/suite/sql_sequence/kill.result

+#
+# MDEV-16929 Assertion ... in close_thread_tables upon killing connection
+# running SHOW on sequence
+#
+CREATE SEQUENCE s ENGINE=InnoDB;
+RENAME TABLE s TO s1;
+connect  con1,localhost,root,,test;
+SHOW CREATE SEQUENCE s1;
+connection default;
+KILL thread_id;
+connection default;
+drop sequence s1;

mysql-test/suite/sql_sequence/kill.test

+--source include/have_innodb.inc
+
+--echo #
+--echo # MDEV-16929 Assertion ... in close_thread_tables upon killing connection
+--echo # running SHOW on sequence
+--echo #
+
+CREATE SEQUENCE s ENGINE=InnoDB;
+RENAME TABLE s TO s1;
+--connect (con1,localhost,root,,test)
+--let $conid= `SELECT CONNECTION_ID()`
+--send
+  SHOW CREATE SEQUENCE s1;
+--connection default
+--replace_result $conid thread_id
+--eval KILL $conid
+
+# Cleanup
+--connection default
+drop sequence s1;

sql/sql_sequence.cc

@@ -485,6 +485,10 @@ int SEQUENCE::read_initial_values(TABLE *table)
       if (mdl_lock_used)
         thd->mdl_context.release_lock(mdl_request.ticket);
       write_unlock(table);
+
+      if (!has_active_transaction && !thd->transaction.stmt.is_empty() &&
+          !thd->in_sub_stmt)
+        trans_commit_stmt(thd);
       DBUG_RETURN(HA_ERR_LOCK_WAIT_TIMEOUT);
     }
     DBUG_ASSERT(table->reginfo.lock_type == TL_READ);