GTID SLAVE

ANALYSIS:
=========
In a MySQL server started with GTID_MODE=ON, concurrent
running of the statements DROP USER and SELECT on
I_S.columns table on multiple threads could lead to a
deadlock.

The INFORMATION_SCHEMA.COLUMNS table provides information
about columns in tables.

DROP USER acquires LOCK_GRANT in mysql_drop_user() and
later acquires LOCK_OPEN on mysql.gtid_executed table.
SELECT on I_S tables acquires LOCK_OPEN on the tables it
tries to fetch information from, in
fill_schema_table_from_frm() and later acquires
LOCK_GRANT. Since the lock order is opposite in these two
queries, a deadlock occurs.

SELECT on I_S table takes LOCK_OPEN before opening the
table in open_table_from_share() and it is released only
after releasing LOCK_GRANT. LOCK_GRANT is acquired for
fetching the necessary column information from the tables.
So LOCK_OPEN was being held for a duration longer than
necessary.

FIX:
====
For SELECT on I_S tables, release LOCK_OPEN immediately
after open_table_from_share() returns.

Change-Id: I04d4e1bc38d4de74d0b99bad3dba43d9cce96168