MDEV 15532 Assertion `!log->same_pk' failed in row_log_table_apply_delete

The reason for the failure is that
thd->mdl_context.release_transactional_locks()
was called after commit & rollback even in cases where the current
transaction is still active.

For 10.2, 10.3 and 10.4 the fix is simple:
- Replace all calls to thd->mdl_context.release_transactional_locks() with
  thd->release_transactional_locks(). The thd function will only call
  the mdl_context function if there are no active transactional locks.
  In 10.6 we will better fix where we will change the return value for
  some trans_xxx() functions to indicate if transaction did close the
  transaction or not. This will avoid the need of the indirect call.

Other things:
- trans_xa_commit() and trans_xa_rollback() will automatically
  call release_transactional_locks() if the transaction is closed.
- We can't do that for the other functions as the caller of many of these
  are doing additional work (like close_thread_tables) before calling
  release_transactional_locks().
- Added missing abort_result_set() and missing DBUG_RETURN in
  select_create::send_eof()
- Fixed wrong indentation in injector::transaction::commit()

sql/sql_class.cc

@@ -4485,7 +4485,7 @@ void destroy_thd(MYSQL_THD thd)
 void reset_thd(MYSQL_THD thd)
 {
   close_thread_tables(thd);
-  thd->mdl_context.release_transactional_locks();
+  thd->release_transactional_locks();
   thd->free_items();
   free_root(thd->mem_root, MYF(MY_KEEP_PREALLOC));
 }