Add declaration of 'refresh_instance_security_rules' to virt driver

The method 'refresh_instance_security_rules' was not defined
in the virt driver ComputeDriver class. In cases where the
underlying virt driver does not support security groups
an exception would be encountered indication that the driver
class does not have the specific attribute.

In addition to adding the method the patch set also catches the
exception NotImplementedError and logs a warning.

Change-Id: Ia36b0dfb54a3ede86467d87f0650a0902adb6d46
Closes-bug: #1269448
Merge "Add declaration of 'refresh_instance_security_rules' to virt driver"