Branch HEAD

Branch HEAD
b=14661
i=green
i=shadow

-- remove BL_AST lock from lru once we mark the lock as a such;
-- do not place BL_AST lock into lru even if the lock is matched and put later;
   => no BL_AST locks in lru at all;
-- CANCELING locks are not so numerous, but to avoid its traversal by another
   thread another time, drop them from the unused list once come them across.