quantum security_group driver queries db regression

The following commit 1c6cc18 removed the populate_security_groups()
method in nova/compute/api.py which causes nova-api to check against the
database if a security group exists.

Fixes bug 1145426

Change-Id: I35a6003ac4c16df364302cf90f701ed977f54946
Merge "quantum security_group driver queries db regression"