Use oslo's strutils for encoding / decoding strings

[Flavio Percoco]

Currently, Glance's client is using its own implementation for encoding / decoding strings. Since this was merged into oslo, it makes sense to use that instead.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/30070

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/30070
Committed: http://github.com/openstack/python-glanceclient/commit/7818387d4ac4c4a20899fc4470da86c5bcabf183
Submitter: Jenkins
Branch: master

commit 7818387d4ac4c4a20899fc4470da86c5bcabf183
Author: Flaper Fesp <email address hidden>
Date: Wed May 22 11:31:25 2013 +0200

    Replace utils.ensure_(str|unicode) with strutils.safe(decode|encode)

    Glanceclient implemented both functions before they landed into oslo.
    Since both functions are already in oslo, it is now possible to pull
    them in.

    There's a small difference between glance's implementation and oslo's,
    that is the later does not convert non-str objects - int, bool - to str
    before trying to decode / encode them. This patch takes care of that
    where necessary, more precisely, while encoding headers before doing a
    new request.

    Fixes bug: #1172253

    Change-Id: I9a0dca31140bae28d8ec6aede515c5bb852b701b