oauth1 downgrade fail with sqlite

[Brant Knudson]

The oauth1 extension migrations fail with sqlite when doing the version 2 downgrade. This is because the migration is attempting to compare a string to an sqlalchemy Engine object.

NotSupportedError: SQLite does not support ALTER TABLE DROP CONSTRAINT; see http://www.sqlite.org/lang_altertable.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/119653

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/119653
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=6ae4d7713ee4d97fb3b52eebe7b833b84c7f3492
Submitter: Jenkins
Branch: master

commit 6ae4d7713ee4d97fb3b52eebe7b833b84c7f3492
Author: Brant Knudson <email address hidden>
Date: Sun Sep 7 15:21:07 2014 -0500

    Fix oauth sqlite migration downgrade failure

    The oauth migration downgrade was failing because it tried to drop
    a constraint which sqlite doesn't support. The code tried to not do
    the drop on sqlite but didn't check for the sqlite engine properly.

    Change-Id: Ie7900d352a26900f913bdefe1eb93d511283efc0
    Closes-Bug: #1366606