domain log WARNING should happen on engine startup

[Steve Baker]

These log warnings would be much more useful to operators if they logged one on engine startup rather than repeatedly during stack execution

2015-03-20 10:31:32.633 WARNING heat.common.keystoneclient [-] stack_user_domain_id or stack_user_domain_name not set in heat.conf falling back to using default
2015-03-20 10:31:32.633 WARNING heat.common.keystoneclient [-] Falling back to legacy non-domain user delete, configure domain in heat.conf

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/166093

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/166093
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=a47639c4a4d71daa2a5a440905614bcaca00fc9c
Submitter: Jenkins
Branch: master

commit a47639c4a4d71daa2a5a440905614bcaca00fc9c
Author: Angus Salkeld <email address hidden>
Date: Mon Mar 23 13:07:39 2015 +1000

    Move stack_user_domain warning to startup

    Add a startup_warnings() function in place to add other
    warnings there if at all possible.

    Change-Id: I4d8d02feccc42c2f3486f52bad488922eb08bbca
    Closes-bug: 1434286