Enable usage of config-drive for file injection

* Some nova deployments allow the use of config-drive to do file
  injection.  Trove, when booting an instance, needs to send this
  to Nova when config-drive is to be used.

Closes-Bug: #1329535

Change-Id: I950b93a32f6c7224f30cf930e5f95710c07cbc26
Fix backup execution workflow

This patch ensures that _run_post_backup() always runs after
the backup operation has completed (post-backup). Fixes issue
wherein any cleanup occuring in _run_post_backup would race
with commands running during backup (potentially unpredictable
dangerous situation).

Change-Id: I279c9a85415ac6ec2ddf8e564a056a3415690f68
Closes-Bug: #1340864
Merge "Enable usage of config-drive for file injection"
Merge "Fix backup execution workflow"