flock.cc: Fix stack allocation from callee used in caller

flock.cc: Fix stack allocation from callee used in caller

	* flock.cc (lockf_t::create_lock_obj_attr): Add buffer parameter.
	Call _everyone_sd with buffer argument from caller rather than
	everyone_sd with locally allocated stack buffer.
	(lockf_t::create_lock_obj): Call create_lock_obj_attr only once
	outside the loop and with additional buffer argument.
	(lockf_t::open_lock_obj): Call create_lock_obj_attr with additional
	buffer argument.