If lock type is LOCK_GAP or LOCK_ORDINARY, and the transaction holds
implicit lock for the record, then explicit gap-lock will not be set for
the record, as lock_rec_convert_impl_to_expl() returns true and
lock_rec_convert_impl_to_expl() bypasses lock_rec_lock() call.

The fix converts explicit lock to implicit one if requested lock type is
not LOCK_REC_NOT_GAP.

innodb_information_schema test result is also changed as after the fix
the following statements execution:

SET autocommit=0;
INSERT INTO t1 VALUES (5,10);
SELECT * FROM t1 FOR UPDATE;

leads to additional gap lock requests.