Sync latest imageutils from oslo-incubator

Performing a sync as imageutils has not been updated since late
in the Icehouse release cycle.

Current HEAD in OSLO:
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commit 36b0e8570b449129d6d474c03b02ceb62edb78df
Date:   Thu Dec 11 11:27:08 2014 +0100
We shouldn't replace `oslo-incubator` in comments

Change being merged with this patch:
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b2d35eec - Use list.pop(0) to keep the code simpler

Change-Id: If15f311db093f05fc97568bdcc5f7ad8ea8abddf
Merge "Sync latest imageutils from oslo-incubator"