ma_pagecache: release lock in pagecache_read
ma_pagecache: release lock in pagecache_read

make_lock_and_pin didn't release the lock so we should.

Found by Coverity (id 972095).

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2