Add mechanism for reporting instance health to cloud platforms about afterburn

[lucab]

@dustymabe indeed, #147 plus #201 fixed this. Closing.

[lucab]

Some more details on cloud reporting protocols.

Packet

A phone-home IP can be discovered from the metadata service. A simple JSON needs to be posted there. We are interested in reporting a "state":"succeeded". This is documented at https://support.packet.com/kb/articles/user-state

Azure

The wire server is provided as a custom DHCP option number 245 (a known/fallback one is at 168.63.129.16). The /machine?comp=health endpoint there expects an XML to be posted with some specific custom headers. The format of that has been reverse-engineered: https://github.com/larsks/azure-tools/blob/master/docs/api.md. We are interested in reporting <Health><State>Ready</State></Health>. The corresponding WALinuxAgent logic is https://github.com/Azure/WALinuxAgent/blob/242278735745483ff63f5001d58ba0889c978936/azurelinuxagent/common/protocol/wire.py#L222

[bgilbert]

The Azure DHCP option is needed for AzureStack and for ASM instances; ARM instances should use a consistent IP.

[arithx]

@lucab: I've posted some relevant info about the Azure check-in along with a simplified bash script + systemd service to perform it in coreos/fedora-coreos-tracker#65

[arithx]

For Azure specifically we might also need to bounce networking.

Ubuntu is cycling networking inside of cloud-init on Azure to DHCP to Azure with the correct hostname so the DDNS is updated for private network communications (which they note mimics what the agent is doing).

[dustymabe]

copying this from coreos/fedora-coreos-tracker#102 (comment)

@dustymabe
I would say so unless it's a much larger work item than I'm currently assuming. You know much more about it than I do so maybe you can clue me in.

@arithx
Overall an initial implementation that doesn't tackle the DHCP option parsing is very straightforward and still covers most use cases of Azure (only missing ASM [legacy] & AzureStack machines).

So we may be able to break out the azure work into two parts. One that does DHCP option parsing and one that does not.

[dustymabe]

was this fixed in #147 ?