Artifacts: public artifact may be modified by any user

[Alexander Tivelkov]

Artifacts should be editable only by their owner and admins. However, is seems like it is not enforced, and if the user has an access to an artifact (e.g. if the artifact is public) she may modify it even without being an admin or artifact's owner.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/218379

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/218379
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=0a9611962d0fb6bdffa9c65c9021ff96972eda90
Submitter: Jenkins
Branch: master

commit 0a9611962d0fb6bdffa9c65c9021ff96972eda90
Author: Alexander Tivelkov <email address hidden>
Date: Fri Aug 28 19:10:04 2015 +0300

    Fixed non-owner write-access to artifacts

    There was no check for write-access priviledges during all the
    mutating operations with artifacts (updates, patches, deletes,
    actiovations etc), so any user who has an access to an artifact could
    modify it. Because of this, non-owners could modify public artifacts
    which was a major security issue.

    Now this is addressed and an appropriate set of tests added to
    prevent possible regressions.

    FastTrack
    Change-Id: I2f4c2d70b74ae39ababed2ba9b97559ef5ea6d6c
    Closes-bug: #1489902