block_device_mapping must be provided if image ref is empty
Add block_device_mapping to all the autoscale fixtures and clients
Fix test_create_scaling_group to pass block_device_mapping to the positive tests
Add negative tests for when an empty image ID is passed without block device mapping
Change system test for bfv to include block_device_mapping
Add block_device_mapping to test_update_launch_config
Change delete_on_termination to True so the volume gets cleaned up when the test server is deleted - thanks @manishtomar
Merge pull request #721 from rackerlabs/bfv-block-device-validation

block_device_mapping must be provided if image ref is empty