Set default CLOUD to 'auto', which will try autodetect the cloud
provider.
Each cloud can have an autodetect script which should print:
<priority> <cloud>
if cloud was detected.
The separate init-early, init-main and init-final were consolidated in
commit 81869cefccd3 (Consolidate init functionality in /sbin/tiny-cloud)
Do the same with the unit tests for those functions.
No functional changes.