Update openstack/common/lockutils

The following commits are in this update:

79e6bc6 fix lockutils.lock() to make it thread-safe
ace5120 Add main() to lockutils that creates temp dir for locks
537d8e2 Allow lockutils to get lock_path conf from envvar

Change-Id: I2190d0aae72ef4a29daf8f7d960da82a33b331b4
Merge "Update openstack/common/lockutils"