Refactor openstack_dashboard tabs.py code

[Lawrance]

In most tabs.py table of openstack dashboard apps, we used hardcode for Tab name and slug which we had defined them in related tables Meta, we could use table meta directly. The bug could be a nice low hanging fruit for new contributors.

https://review.openstack.org/#/c/196341/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/196341
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=564d912e697da0679d1ad96d344f59389616d6c2
Submitter: Jenkins
Branch: master

commit 564d912e697da0679d1ad96d344f59389616d6c2
Author: jingliuqing <email address hidden>
Date: Sat Jun 27 13:09:44 2015 +0800

    Refactor the admin tabs code

    Partial-Bug: #1475119
    Change-Id: I3329a09fee2b472ac50bd409e3c5613926d1e39f

[Rob Cresswell (robcresswell-deactivatedaccount)]

A better solution may be just to set the default on the TableTabs.

[Rob Cresswell (robcresswell-deactivatedaccount)]

Removed assignee due to inactivity.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/307533

[OpenStack Infra (hudson-openstack)]

Change abandoned by David Lyle (<email address hidden>) on branch: master
Review: https://review.openstack.org/307533
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.