Add security group configuration for Hyperv agent

Hyperv agent of Neutron has supported security group.
Please refer to: https://review.openstack.org/#/c/74199/
Adding security group configuration for Hyperv agent
to avoid Neutron Hyperv agent startup errors if
no security group set in configuration file.

Change-Id: Ifccfc744729f4cde897e79ce5afd2e3bd5b292a2