'create temporary table as select' generates unnecessary table locks

A 'create temporary table as select' statement seems to produce an unnecessary table lock (which applies across all connections) against the table identifier. This can cause deadlocks in a simple case and in the more complex case (where the select is marked 'for update') can produce a ER_LOCK_WAIT_TIMEOUT error. Attached is a sql script to set up the database for reproduction. Call the procedure `sp_test` from two connections to see the error.

Breaking the statement into separate 'create' and 'insert' statements produces the expected locking behaviour whereby neither thread is held up.

Tested against mariadb 10.1.17 on ubuntu 16.04.1 LTS.