MDEV-22881 Unexpected errors, corrupt output, Valgrind / ASAN errors in Item_ident::print or append_identifier

After this code

end_inplace:

  if (thd->locked_tables_list.reopen_tables(thd, false))
    goto err_with_mdl_after_alter;

table is not reopened (need_reopen is false) but
some_table_marked_for_reopen is reset to false.

Item_field is allocated on table lock and assigned new name on first
ALTER which is then freed at the end of the command. Second ALTER
accessess this Item_field and gets garbage value.