Check for deleted networks associated with live-images

OS-276

Live-images keep track of the networks that were attached to the
original instance. These networks are attached at launch by default
and can be optionally overridden. Previously there was no check that
these networks still existed in the system. If the network did not
exist, then no network information could be allocated to the instance
causing it to fail at launch time.

This patch now checks for the validity of the networks associated with
the live-image before attempting the launch.

Change-Id: Ifd4e4d951fa9f92d4b31675c1f11e5e58eb4171c
Trivial fixup to instance_update parameters (instance vs instance_uuid)

Seems like a merge, or a couple of them, resulted in some incorrect
usage of the _instance_update method. This patch is a sweep to clean
up all the incorrect usage of passing in the instance_uuid.

Change-Id: I68ff6e4d7512f3a8597d7c389620ee0990e0c0cb
Merge 'Check for deleted networks (OS-276)' into havana/1.5

Conflicts:
	cobalt/nova/extension/manager.py

Change-Id: I8959ad2a501dcf1e6c2576cb43421b320e427833
Merge remote-tracking branch 'origin/havana/1.5' into up_ice5

Change-Id: I4dd1ed4cfb41c63342b40199a20f345ddd16b157