Generic CloudConfig drive

[olivierlambert]

Currently, the cloudconfig drive is only used with the Citrix Docker plugin (they are both in the same plugin, despite they are different thing). But the XScontainer plugin can't work for other distro, see xenserver/xscontainer#22

Ideally, we should wait for having this part (cloudconfig) as a first class citizen in the XAPI.

Nevertheless, it's also possible to create a disk ourselves.

• create a createCloudInitConfigDrive(vmId,srId,config) in the server
  • create a 10MB disk in XAPI
  • import a RAW VDI inside it in FAT format
  • attach it to the VM
• modify the UI in XO to expose a cloudconfig panel to activate for Templates with disks
  • display the list of existing template disks
  • allow growing of existing disks (if cloud is activated)
  • possibility to change disk name and description
  • choose SR of existing disks
  • allow add extra disks
• expose CloudInit options directly in the UI:
  • enable or disable the cloud config panel with a switch in the panel heading (on top right)
  • if disabled, display clearly at the end of the panel content: "Cloud config is disabled", and the opposite message if enabled
  • hostname, autofilled with vm name? (hostname:) fill with the VM name by default
  • SSH keys (ssh_authorized_keys:)