Latest cherry-picked changes for Dogwood.

Seems like we stopped using devpi with #971 two years ago.

Cherry-picked from commit 11d696b1.

Cherry-picked from master.

If a git version is specified as a branch, and the commit referred to is
already on the local working tree, but the branch is not, then the
checkout will fail.

This is because the Ansible 1.9.3 module would check to see if the
commit was already present, and if so, did not fetch. This meant the
branch wasn't defined in the local working tree.

This can happen if you make a branch but there aren't any changes on the
branch.

Pin IDAs to OPENEDX_RELEASE, and remove edx-notes-api from native install

Just ensure the file is gone.

The older chrome repositories have been taken down; however, we
use a saved copy of the debian package. After installing that package,
ensure it is not referenced by the target machine after Chrome
is installed.

Dogwood final box names

Add two more management commands, and make manage.py invocation uniform

Add the forums migration for teams discussion filtering

Ned/unhandle certs xqueue

Pip 8.0.0, released a few hours ago, tries to uninstall deb-installed
python modules that it wants to upgrade, and always fails when doing so.
The effect is that configuration/requirements.txt cannot be fulfilled,
notably ansible 1.9.3-edx, which requires an upgrade to pycrypto.

This forces the installation of pip to the latest one prior to 8.0.0,
7.1.2.

It also freezes setuptools and virtualenv, so that they should all match
the current versions required on
playbooks/roles/common_vars/defaults/main.yml:common_pip_pkgs.

Dogwood upgrade automation

Upgrading to Dogwood is complicated, because we have to make two
intermediate stops along the way: once at the end of Django 1.4 to
migrate the databases using South, then to the beginning of Django 1.8
to apply --fake-initial migrations.  Then we can upgrade to the Dogwood
release that we actually want.