Allow lockutils to get lock_path conf from envvar

This would allow us to provide a common dir for all locks in all
processes involved in testing or running software.

Change-Id: I64fccddc92ada67a3df6daf86d73750a41bbce05
Add main() to lockutils that creates temp dir for locks

This change would allow us to create one directory to store all locks
from all processes involved in testing in projects.

Here are examples on how to use this:
Heat - https://review.openstack.org/47360
Ceilometer - https://review.openstack.org/44809
(see tox.ini)

Change-Id: I9e1260e202b7d8feb9c762a879b9804ed85ccbd6
Merge "Allow lockutils to get lock_path conf from envvar"
Merge "Add main() to lockutils that creates temp dir for locks"