azure: add udev rules to create cloud-init Gen2 disk name symlinks
Cloud-init delivers udev rules on Azure to create the following symlinks:
- /dev/disk/cloud/azure_root
- /dev/disk/cloud/azure_root-part#
- /dev/disk/cloud/azure_resource
- /dev/disk/cloud/azure_resource-part#
Cloud-init cc_disk_setup expects presence of these dev links in order to
setup the mounted ephemeral disks. Gen1 instances udev rules match based
only a DEVICE_ID attribute that no longer exists on Gen2 instances.
Supplement existing Gen1 rules with matches on specitic SCSI target/lun
path 0:0:0 and 0:0:1 and generate links for azure_root and azure_resource
respectively.
azure: report ready to fabric after reprovision and reduce logging
When reusing a preprovisioned VM, report ready to Azure fabric as soon as
we get the reprovision data and the goal state so that we are not delayed
by the cloud-init stage switch, saving 2-3 seconds. Also reduce logging
when polling IMDS for reprovision data.
instance-data: fallback to instance-data.json if sensitive is absent.
On cloud-init upgrade path from 18.3 to 18.4 cloud-init changed how
instance-data is written. Cloud-init changes instance-data.json from root
read-only to redacted world-readable content, and provided a separate
unredacted instance-data-sensitive.json which is read-only root.
Since instance-data is only rewritten from cache on
reboot, the query and render tools needed fallback to use the 'old'
instance-data.json if the new sensitive file isn't yet present.
This avoids error messages from tools about an absebt
/run/instance-data-sensitive.json file.
