only pass stack id to init stacklock is enough

[Ethan Lynn]

For most of time, stack id is enough for class stacklock, only acquire() function need other information of stack.
It's better to lazy load stack when necessary.

https://github.com/openstack/heat/blob/b4a0ee8bafad55cbc59498a4a43383ed26ef6713/heat/engine/stack_lock.py#L88-L89

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/171930

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/171930
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=0b59af6acc0ce8cc664b5977835ecafe23c4f5f1
Submitter: Jenkins
Branch: master

commit 0b59af6acc0ce8cc664b5977835ecafe23c4f5f1
Author: Ethan Lynn <email address hidden>
Date: Thu Apr 9 13:25:19 2015 +0800

    Pass stack id to init stacklock

    Only acquire() function in stacklock needs to load whole stack,
    other function only needs stack id. This patch only pass
    stack id for stacklock so that in some place we don't need
    to load whole stack.

    Change-Id: Iaad5f4a871f925c4052d159a5d95184681d5bd28
    Closes-Bug: #1441972