Migration DB_INIT_VERSION in common place.

[Ilya Pekelny]

Common code and tests use migrations. Init version value exists only in migration_helpers. It could be a good improvement to move DB_INIT_VERSION into a common place to have access from any place of the project.

[Openstack Gerrit (openstack-gerrit)]

Fix proposed to branch: master
Review: https://review.openstack.org/88016

[Openstack Gerrit (openstack-gerrit)]

Reviewed: https://review.openstack.org/88016
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=3c6edad94444675999ac82b1fda8342af4bbd833
Submitter: Jenkins
Branch: master

commit 3c6edad94444675999ac82b1fda8342af4bbd833
Author: Ilya Pekelny <email address hidden>
Date: Wed Apr 16 18:48:02 2014 +0300

    Migration DB_INIT_VERSION in common place

    Init version value exists only in migration_helpers. migration_helpers
    shouldn't know nothing about migrate repos, primarily because it is
    intended for handling of any migrate repo in the project.

    Change-Id: I8bceea0cf5eaf8e623efbb39e385b1990eca0a6f
    Closes-Bug: #1308593