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
use "rabbit_hosts" config option instead of "rabbit_host"

This allows for easy client configuration against clustered RabbitMQ
setups.  Does not break existing configs.

Change-Id: I2b180f8860a727e35d7b465253689e5e8c44eb98
Closes-Bug: 1286411
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
Adds support for IBM SDN-VE Neutron plugin

This provides the support for the monolithic plugin
for IBM SDN-VE that is being added to Neutron here:
https://review.openstack.org/#/c/66453/

Implements: blueprint ibm-sdnve-plugin-support
Depends-On: I92619a95bca2ae0c37e7fdd39da30119b43d1ad6
DocImpact

Change-Id: I0958457355036fdab93156cd7fb4afd1a458918b
Merge "use "rabbit_hosts" config option instead of "rabbit_host""
Merge "Adds support for IBM SDN-VE Neutron plugin"
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"