Sync oslo.incubator modules

Update the oslo.incubator modules needed. Due to internal oslo
dependencies, strutils has been also imported.

Change-Id: I8cc1eb0003520a2d3b697c4d584c7c96aa5401d6
Updated from global requirements

Change-Id: Ie026a6037e02c0ddfb5c4ccb7dbf183b030d626c
Fix requests version for build scripts

Global requirements specifies a different version of requests
than we do in these build scripts. Fix this temporarily; in the
future the build scripts should use the requirements.txt file
at the root.

Change-Id: I3f03f8a5a34a2a23ff4f76de7a73289cf4d769ff
Cleanup coreos-oem-inject.py

The current script used to inject the IPA container into CoreOS is
not pep8 compliant, has requirements that are not in
global-requirements, and never has tests run. Now requirement on
plumbum is removed, script is pep8 compliant, flake8 runs against the
script when tests are run.

Closes-bug: #1337551

Change-Id: I14d3e46e60c4e072f34f80dc50d7214079953f49
Use requirements.txt from the root for image build

This ensures that the requirements.txt used for building images
is kept in sync with global requirements.txt.

Change-Id: Id474a8de4798ed4fbc56e7133073d8a674ec4f84
Merge "Updated from global requirements"
Merge "Sync oslo.incubator modules"