refactor: move RawTGZImage and UpdateGlanceImage to common

[Mate Lakat]

Once https://review.openstack.org/40909 is merged, move RawTGZImage to a common library, so others can re-use it.

Also consider moving UpdateGlanceImage:

https://review.openstack.org/41651

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/46056

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/46057

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/46056
Committed: http://github.com/openstack/nova/commit/0b0dfd289196d9ec8cdc527327ba038820dd1b0d
Submitter: Jenkins
Branch: master

commit 0b0dfd289196d9ec8cdc527327ba038820dd1b0d
Author: Mate Lakat <email address hidden>
Date: Wed Sep 11 12:13:53 2013 +0100

    xenapi: refactor: move UpdateGlanceImage to common

    During the review of https://review.openstack.org/41651 it was
    recommended to move UpdateGlanceImage to a common library. A bug was
    filed to deal with the refactors. This change fixes the first part.

    Fixes bug 1220596

    Change-Id: I95ae89525b7e6768c5a70364945d5a10cb906d88