Resolved following issues :
1) Added port security extension while configuring neutron for NFP,
2) Corrected polling time calculation in nfp_node_driver,
3) Explicitly making a dhcp request whenever service vm comes up,
4) Corrected svc_management group creation, to use different l3 policy
for gate tests.
Change-Id: I2e88103c174ce864f618c0eb4e0202dcb500a4fa
Closes-Bug: 1663134