Convert ovs-bridge module to python

Vagrant runs were failing on 'ovs br-int'. On the surface it looked like
this call was hanging in ruby. Therefore, I moved this module to python.
Turns out that this was not the root cause, but the work was already
done.

!version-minor
Merge pull request #518 from craigtracey/ovs-bridge-python

Convert ovs-bridge module to python