Asynchronous solution of
MDEV-17554 has drawback of race condition:
1. statement thread unlocks table, finishes execution;
2. table is dropped, new table with same name is created;
3. alter thread tries to add partition to new table.
The worst consequence: new table has additional partition unexpectedly.
Instead of asynchronous thread make direct `fast_alter_partition_table()` call at the finish of DML statement.