Add rootwrap filters for ofagent

neutron-ofagent-agent currently relies on the fact the rootwrap
filters for neutron-openvswitch-agent covers what it needs.
as they are independent agents and their requirements are
getting more different, introduce a dedicated rootwrap filters
for ofagent.

Closes-Bug: #1392560
Change-Id: Iba205260a238431432caf8d9697268ceeef85eca
Merge "Add rootwrap filters for ofagent"