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
Merge "Enable usage of config-drive for file injection"