Clean up configure_nova() a bit

Change-Id: I2228221051a5a4413a34ca359856d90794fce69a
Refactor init functions to simplify Grenade upgrades

* Glance: create_glance_cache_dir()
* Cinder: create_cinder_cache_dir() and create_cinder_volume_group()
* Nova: create_nova_cache_dir() and create_nova_keys_dir()
* Random tidy-up changes

Change-Id: I20d995d4c2e5facfb912ee03a6cda6c56f20bbe9
Merge "Clean up configure_nova() a bit"
Merge "Refactor init functions to simplify Grenade upgrades"