Revert "ovs-agent: Ensure integration bridge is created"

This reverts commit e5cdad90f97d3a54a493eca19e7a3ff643426de1.

TripleO's multi-node testing shows that this patch caused a failure to receive
tunnel updates, leading to the first node up to have no agent ports, the second
to have one agent port, the third to have 2 agent ports, etc. Needless to say,
this doesn't work all that well :)

Change-Id: Ie90dd4d113a404948dd5debad48065b7db48faa5
Closes-Bug: #1292105
Merge "Revert "ovs-agent: Ensure integration bridge is created""