Configure privsep in SR-IOV agent

With the introduction in [1] of commands executed under a privsep
context, privsep should be initialized first.

[1]https://review.opendev.org/#/q/6f7b88d0808bee36b9d089ce8d3c0f98ae0b2dea

Change-Id: Ifdb8ad910ff6ffb31668ebb1e97d885ee924b470
Closes-Bug: #1883757

neutron/plugins/ml2/drivers/mech_sriov/agent/sriov_nic_agent.py

@@ -44,6 +44,7 @@ from neutron.api.rpc.handlers import securitygroups_rpc as sg_rpc
 from neutron.common import config as common_config
 from neutron.common import profiler as setup_profiler
 from neutron.common import utils as n_utils
+from neutron.conf.agent import common as agent_config
 from neutron.plugins.ml2.drivers.mech_sriov.agent.common import config
 from neutron.plugins.ml2.drivers.mech_sriov.agent.common \
     import exceptions as exc
@@ -547,6 +548,7 @@ def main():
     common_config.init(sys.argv[1:])
 
     common_config.setup_logging()
+    agent_config.setup_privsep()
     try:
         config_parser = SriovNicAgentConfigParser()
         config_parser.parse()