Use default value during update

[Sergey Kraynev]

There are a lot of properties have default value in property schema.
This default variables are used during stack creation, but are not used during update.

For example:
1 . property has default value [].
2. you create stack nd set this property in [val1, val2]
3. then you want to update stack using template without this property.
Expected behavior will be use default value in this case, but currently you will get value equal None.

I suppose we should chose what variable will be used during update (value from prop_diff or default value )

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/83709

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/84400

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/83708
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=08b702d4c31e7a87ff5fa38b9ace795942e0c05a
Submitter: Jenkins
Branch: master

commit 08b702d4c31e7a87ff5fa38b9ace795942e0c05a
Author: Sergey Kraynev <email address hidden>
Date: Fri Mar 28 06:16:12 2014 -0400

    Fix incorrect logic during updating in unittest

    The property image_update_policy has two ways for initialization during
    update. One of them is when image_update_policy is not presented in
    prop_diff and shoud be used from self.properties. So image_update_policy
    should be used in old and new templates without any changes.

    Related-Bug: #1298850
    Change-Id: Ie9afa65ad6d095d4293be077536fb807919de789

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/83709
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=fcecf91840d8ac12e00dc2ff9f95f4e5066684e7
Submitter: Jenkins
Branch: master

commit fcecf91840d8ac12e00dc2ff9f95f4e5066684e7
Author: Sergey Kraynev <email address hidden>
Date: Fri Mar 28 06:50:44 2014 -0400

    Using default value during update

    At the current moment default value is used only during resource
    creation. However It should be used during update too.

    Change-Id: I385d48b65f475284c80d2678cf83ce9dae1d76e3
    Closes-Bug: #1298850