Use new images when spawning BM instances.

With nova-BM the TFTP files (kernel and ramdisk) are cached between
instances but disks never are (today). We were treating the disk image
the same way but this is incorrect because its filename is 'disk'
rather than '$uuid' and as such it has to be cleaned out whenever a
deploy request is being processed.

Change-Id: I15c8fc25a4c064341b9f1ed51e6df8d1494fbdff
Co-Authored-By: Robert Collins <rbtcollins@hp.com>
Avoid deadlock when stringifying NetworkInfo model

In the libvirt driver, we log information about the instance we're
about to generate XML for, which includes a NetworkInfo model. In
reality, this is a NetworkInfoAsyncWrapper which acquires a lock
on the model. Since we're in the middle of a log statement, we also
hold the logging lock. This happens right after we've fired off an
async request to update information about the instance, which first
acquired the network model lock and then acquired the logging lock
to make a seemingly innocuous log record.

The resulting deadlock is fixed by this patch by stringifying the
NetworkInfo object before making the log call in the libvirt
driver.

Change-Id: I81f35197ab7c74daa84fb51fbaa2df28c025da13
Closes-bug: 1276268
Merge "Avoid deadlock when stringifying NetworkInfo model"
Merge "Use new images when spawning BM instances."