`unstack.sh -a` does not stop rabbitmq/mysql

[Mike Chester]

According to the comment at the top of the unstack.sh file in devstack, specifying UNSTACK_ALL or -a should stop both mysql/postgres/rabbitmq, but it does not.

Looking at the code it appears as though if you specify `-a` UNSTACK_ALL will be set to an empty string which fails the check on whether the script needs to stop the services.

The script also does not take into account any environmental values being set for UNSTACK_ALL as it is set to an empty string on line 12.

This occurs in stable/kilo stable/liberty and master branch

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/281468

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/281468
Committed: https://git.openstack.org/cgit/openstack-dev/devstack/commit/?id=8040e69a049731216efcdc3497b78391f7bc2a31
Submitter: Jenkins
Branch: master

commit 8040e69a049731216efcdc3497b78391f7bc2a31
Author: Mike Chester <email address hidden>
Date: Wed Feb 17 10:52:33 2016 -0800

    Check UNSTACK_ALL or -a flag set on unstack

    These flags were not functioning as described. Check if UNSTACK_ALL is
    set in env or -a flag is set when calling script.

    Change-Id: I128d32b1e74ee46e24a9eb2e81560e58137b1553
    Closes-Bug: #1546687