Glance v2: Image property quotas are unforgiving when quota is exceeded

One proposal, I think can we add a function to db, just like what you did at [1], and use that to check and skip quota checking if user required to remove a property but add at [2].

[1] https://github.com/openstack/glance/blob/master/glance/db/sqlalchemy/api.py#L1082
[2] https://github.com/openstack/glance/blob/master/glance/quota/__init__.py#L58

Fix proposed to branch: master
Review: https://review.openstack.org/63674

Reviewed: https://review.openstack.org/63674
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=0d95e5316a99b78b4f629a29d862548f87671b43
Submitter: Jenkins
Branch: master

commit 0d95e5316a99b78b4f629a29d862548f87671b43
Author: David Koo <email address hidden>
Date: Mon Dec 23 14:09:41 2013 +0800

    Allow some property operations when quota exceeded

    Currently in Glance v2 if, for some reason, an image has more
    properties than the image_propery_quota allows (e.g. the quota was
    lowered after the image was created with properties) then any request
    to modify or delete existing properties results in a 413 overlimit
    error. Ideally a user should be able to remove properties or any other
    action except for adding a property when they are over their quota for
    a given image.

    This commit does this by adding a new member to the quota.ImageProxy
    class to "remember" what properties were already present in an image
    *before* any new property operations are preformed on the image. After
    the new property operations are performed the quotas are checked (before
    writing the image info to DB) only if any new properties have been
    added.

    This commit does not use a subclass of ExtraPropertiesProxy to check
    property quotas (in the __setitem__ method) because Glance does not
    implement the JSON-patch RFC correctly - in Glance all operations in a
    patch are applied and the quota checked only after all operations have
    been applied (RFC requires that operations be applied sequentially and
    fail on the first failure). Therefore it is possible for the quota to be
    temporarily exceeded when a patch is being applied and therefore we
    cannot check for quotas as they are being added - we have to wait until
    all patch operations have been completed.

    Also, as per review discussions in IRC, a new file:
        glance/tests/integration/v2/test_property_quota_violations.py
    has been added to perform image property quota related tests (because
    the functional test framework is slow).

    Change-Id: Icf1b46343463791ed3d2f3ce376f11e409e792ff
    Closes-bug: #1258331
    Author: David Koo <email address hidden>