Exit rpc_loop when SIGTERM is recieved in ovs-agent

Previously ovs-agent exited with exit code 1 after SIGTERM was received.
SIGTERM should shutdown agent gracefully and exit code should be 0.

Closes-Bug: #1334264
Change-Id: I23e81cee5ae9e9fdabbe1377420b0902f47be8a7
Add config for performance gate job

This rally scenario is intended to be run in OpenStack CI
by rally-dsvm-neutron-neutron job.

Implements: blueprint neutron-performance-gate-jobs
Closes-Bug: #1334434
Change-Id: If204f3dfc32933792d09fdc929c248fc3f17b0bc
Merge "Add config for performance gate job"
Merge "Exit rpc_loop when SIGTERM is recieved in ovs-agent"