This change will first attempt to get ec2 metadata from a v2 config
drive before falling back to the nova metadata server if no config
drive is detected.
Config drive is enabled in overcloud nodes, so using this for
os-collect-config will allow the undercloud nova metadata server to be
disabled.
V2 of the config-drive was released in OpenStack Folsom, so a decision
was made to not support V1 discovery at all. This makes the block
device candidate selection much simpler than the cloud-init one[1].
[1] https://git.launchpad.net/cloud-init/tree/cloudinit/sources/DataSourceConfigDrive.py#n219
Change-Id: I2aec0544fe40c2e901aee38c79bb838a627d20da
Closes-Bug: #1619074
76975f04e5