In 'tomoyo_delete_domain', return -EINTR if locking attempt is
interrupted by signal.
At present it returns success to its caller 'tomoyo_write_domain()'
even though domain is not deleted. 'tomoyo_write_domain()' assumes
domain is deleted and returns success to its caller. This is wrong behaviour.
'tomoyo_write_domain' should return error from tomoyo_delete_domain() to its
caller.