Sync latest strutils from oslo-incubator

We have had a request from Tristan Cacqueray to pull in the latest
strutils.  The request is driven by a need to get improvements in
place that make strutils.mask_password more secure.

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Head of oslo-incubator:
commit 80a08a413fb0f23a056eca2d273b167f0a09bab6
Merge: 83c4098 d73f3b1
Author: Jenkins <jenkins@review.openstack.org>
Date:   Mon Aug 25 14:32:36 2014 +0000

    Merge "Remove unused/mutable default args"

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This sync pulls in the following change:

66142c34 - Make strutils.mask_password more secure

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Change-Id: Ie51d316a30bed40996db6cd860dbb9cb173e5ac6
Partial-bug: 1345233
Merge "Sync latest strutils from oslo-incubator"