Clean up "target" interface to policy

The docstring is wrong for this argument, and we pass an empty
dict since we're not using this data for policy decisions at
the moment, so default it inside common.policy.Enforcer.

Change-Id: I298e691e12ed10825327492f02bd2f4edec24323
test_common_policy cleanups

Make test_common_policy.py a bit less repetitive, and ensure
VerifyAll is used consistently via cleanup

Change-Id: Ic7f017661d034c1968a6888c03c7492db9c47b3f
Implement PrivateIpAddress attribute

The PrivateIpAddress attribute maps to the private IP address of the
AWS::EC2::NetworkInterface resource.

Change-Id: I471e9ab9ea6fed8bc09a6339d11bcf1f1e4528f8
Closes-Bug: #1254675
Merge "Clean up "target" interface to policy"
Merge "test_common_policy cleanups"
Merge "Implement PrivateIpAddress attribute"