Delete image when backup operation failed on snapshot step

when we snapshot an instance, we will use @delete_image_on_error to
delete any failed snapshot, however, the image will not be removed
by backup code flow, it will be an issue if too many backup failed
at last ,all useful image will be removed and we have only 'error'
image left in host

Change-Id: Ib527ade86aef52a8445b57fa03fed434578c4204
Closes-Bug: #1288574
Network: add instance to the debug statement

Allocating and deallocating a network from an instance needs
more info to debug especially when more than one instance
has the same name.

The same change is also made regarding exceptions. That is,
the instance UUID will be used instead of the name.

Change-Id: I624fe77c71f6cb7ca453c863b59f0452c8e6b383
Make sure domain exists before referencing it

Before calling domain.destroy() in the exception handler for a failed
create attempt, make sure domain was created prior to when the
exception was thrown.

Change-Id: I3b7c5afce7f3bacce1b444c245b035334962ff7c
Closes-Bug: #1326998
Don't translate debug level logs in nova

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).

This is the final patch ensuring that all fines in the nova directory
no longer have translations for debug messages.

Change-Id: Ib10f5826e2238cbb2d4315c48be570eb31b2ea55
Merge "Don't translate debug level logs in nova"
Merge "Network: add instance to the debug statement"
Merge "Make sure domain exists before referencing it"
Merge "Delete image when backup operation failed on snapshot step"