MDEV-20471 Assertion during cleanup of failed CREATE TABLE LIKE <sequence>

While cleaning up a failed CREATE TABLE LIKE <sequence>, `mysql_rm_table_no_locks`
erroneously attempted to remove all tables involved in the query, including
the source table (sequence).

Fix to temporarily modify `table_list` to ensure that only the intended
table is removed during the cleanup.

mysql-test/main/sequence_debug.result

+#
+# MDEV-20471 Assertion during cleanup of failed CREATE TABLE LIKE <sequence>
+#
+CREATE SEQUENCE s;
+set @save_debug_dbug=@@debug_dbug;
+set debug_dbug='+d,kill_query_on_sequence_insert';
+CREATE TABLE t LIKE s;
+ERROR 70100: Query execution was interrupted
+DROP TABLE t;
+ERROR 42S02: Unknown table 'test.t'
+DROP SEQUENCE s;
+set debug_dbug=@save_debug_dbug;

mysql-test/main/sequence_debug.test

+--source include/have_debug.inc
+
+--echo #
+--echo # MDEV-20471 Assertion during cleanup of failed CREATE TABLE LIKE <sequence>
+--echo #
+
+CREATE SEQUENCE s;
+set @save_debug_dbug=@@debug_dbug;
+set debug_dbug='+d,kill_query_on_sequence_insert';
+--error ER_QUERY_INTERRUPTED
+CREATE TABLE t LIKE s;
+--error ER_BAD_TABLE_ERROR
+DROP TABLE t;
+
+DROP SEQUENCE s;
+set debug_dbug=@save_debug_dbug;

sql/sql_sequence.cc

@@ -300,7 +300,8 @@ bool sequence_insert(THD *thd, LEX *lex, TABLE_LIST *org_table_list)
   Query_tables_list query_tables_list_backup;
   TABLE_LIST table_list;                        // For sequence table
   DBUG_ENTER("sequence_insert");
-
+  DBUG_EXECUTE_IF("kill_query_on_sequence_insert",
+                  thd->set_killed(KILL_QUERY););
   /*
     seq is 0 if sequence was created with CREATE TABLE instead of
     CREATE SEQUENCE

sql/sql_table.cc

@@ -5306,7 +5306,14 @@ int mysql_create_table_no_lock(THD *thd, const LEX_CSTRING *db,
     if (res)
     {
       DBUG_ASSERT(thd->is_error());
-      /* Drop the table as it wasn't completely done */
+      /*
+        Drop the new table, we were not completely done.
+
+        Temporarily modify table_list to avoid dropping source sequence
+        in CREATE TABLE LIKE <SEQUENCE>.
+      */
+      TABLE_LIST *tail= table_list->next_local;
+      table_list->next_local= NULL;
       if (!mysql_rm_table_no_locks(thd, table_list, 1,
                                    create_info->tmp_table(),
                                    false, true /* Sequence*/,
@@ -5320,6 +5327,7 @@ int mysql_create_table_no_lock(THD *thd, const LEX_CSTRING *db,
         */
         res= 2;
       }
+      table_list->next_local= tail;
     }
   }