DescribeInstances in ec2 shows wrong image-message

If one instance boots from a volume,
the value of 'image_id' by 'DescribeInstances' in ec2,
will be a wrong number.

The value of 'image_ref' for this type of instances, is '', not None.
So the original protected codes can't take efforts.

Change-Id: I8c5e1c626f2b7873e7720f3615db1ee1ec6c681a
Closes-Bug: #1278696
Fix bad param name in method docstring

Fix tiny nits in a couple of methods.

Change-Id: I327bd78d232ffd5c8d2d1dd60724397430192a61
Don't translate debug level logs in nova.network

Our translation policy
(https://wiki.openstack.org/wiki/LoggingStandards#Log_Translation) calls
for not translating debug level logs. This is to help prioritize log
translation. Furthermore translation has a performance overhead, even if
the log isn't used (since nova doesn't support lazy translation yet).

Change-Id: I8973992d0dd2348f9c657c3caa1cc9c7d79a4c7b
Merge "Fix bad param name in method docstring"
Merge "DescribeInstances in ec2 shows wrong image-message"
Merge "Don't translate debug level logs in nova.network"