Use joinedload for system_metadata in db

When moving over to nova.db.api not returning sqlalchemy
objects, objects won't be lazy loaded throughout the code, instead the
entire object will be fetched from the DB in nova.db.api.  This change
will trigger any lazyload bugs due to missing joinedload statements
that weren't previously triggered because the lazyloaded data wasn't
being used (and thus fetched from the DB).

Partially implements bp db-api-cleanup

Change-Id: I0dabf3588be0076a6e651c018a1c83ed23e84872
add config drive to api_samples

Add config drive extension show and details to api_samples

blueprint nova-api-samples
bug 1091737

Change-Id: I6ae1f01a417f153723b85d08c2f181909c154946
Remove a log message in test code.

This log message indicates that this code should only run during
testing.  The downside is that it does run during testing and can cause
a bunch of annoying noise in test logs.  Just remove it.

Change-Id: I2cc18f3b7871dbfa8859e33225fb7c2bb1ccc53b
Merge "Remove a log message in test code."
Merge "Use joinedload for system_metadata in db"
Merge "add config drive to api_samples"