Support image property for config drive

Currently Nova decides the config_drive based on user input and compute
node configuration. We should also consider the image requirement for
config drive.

Implements: blueprint config-drive-image-property

DocImpact:
    An new image metadata support added.

Change-Id: Ica32fb078d5440dbcf1251175585d34af9549815
Merge "Support image property for config drive"