AVAILABLE_REGIONS setting name gets confused with regions within Keystone service catalog

[Timur Sufiev]

Currently we have 2 different kinds of regions: the service regions inside Keystone catalog and AVAILABLE_REGIONS setting inside
Horizon, yet use the same name 'regions' for both of them. That creates a lot of confusion when solving some region-related issues at the Horizon/Keystone junction, even explaining what is exactly being broken poses a serious challenge when our common language has such a flaw!

I propose to invent 2 distinct terms for these entities, so at least we won't be terminologically challenged when fixing the related bugs.

According to the discussion in ML (see http://lists.openstack.org/pipermail/openstack-dev/2015-July/068917.html), the name 'AVAILABLE_KEYSTONE_ENDPOINTS' was chosen as a proper replacement.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/222131

[OpenStack Infra (hudson-openstack)]

Change abandoned by Timur Sufiev (<email address hidden>) on branch: master
Review: https://review.openstack.org/222131
Reason: Change-id should not be the same as dependency commit

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/222132

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/224759

[OpenStack Infra (hudson-openstack)]

Change abandoned by Timur Sufiev (<email address hidden>) on branch: master
Review: https://review.openstack.org/222132
Reason: Moved into https://review.openstack.org/#/c/224759/

[OpenStack Infra (hudson-openstack)]

Change abandoned by David Lyle (<email address hidden>) on branch: master
Review: https://review.openstack.org/224759
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Rob Cresswell (<email address hidden>) on branch: master
Review: https://review.openstack.org/224759
Reason: Due to inactivity and merge conflict