devstack (stack.sh) fails when extra config files are specified

Latest merge of https://review.openstack.org/#/c/71996/ exposes an issue
in stack.sh which did not surface before.

Please see the details of the issue in the bug description.

Closes bug: 1285884

Change-Id: Ie231c9835497c2a418a61d339dfd5df1aab9e3d7
Remove bm_poseur, unmaintained and obsolete

The bm_poseur git repository link has been broken
for over 11 months. The virtualized/fake baremetal
environment is not working and has not worked in a
long time. Now, on the tail of enabling 'enable -o errexit',
this functionality now has a hard break.

Change-Id: I3cbd8db58c422bc5273d2433278aaa5e449ecfd9
Closes-Bug: 1285954
Add configurations for the OpenFlow Agent mechanism driver

This patch supports configurations for an environment of the OpenFlow Agent mechanism driver
Set the following variables in a localrc to be ran this mechanism driver.

Q_ML2_PLUGIN_MECHANISM_DRIVERS=ofagent
Q_AGENT=ofagent

Implements: blueprint ryu-ml2-driver
Change-Id: I774da9a26f241487dfa4ec124b12f528704d860b
Fix pep8 errors

This commit fixes pep8 errors.

Change-Id: Ia1f1d61081a86b8a58251918392171cbc60f5ab8
Merge "Remove bm_poseur, unmaintained and obsolete"
Merge "Add configurations for the OpenFlow Agent mechanism driver"
Merge "devstack (stack.sh) fails when extra config files are specified"
Merge "Fix pep8 errors"
Merge branch 'master' of https://github.com/openstack-dev/devstack