Adds support for security_groups for V3 API server create

Adds support for specifying the security group during the V3 API
server create to the security groups extensions. This was
accidentally missed during the initial port. Adds the
corresponding XML deserialization and unittests.

Partially implements blueprint nova-v3-api
Fixes bug #1208746

Change-Id: Ie9d9e03ae20357212b0f270d97a19a0d0f9b0557
Merge "Adds support for security_groups for V3 API server create"