Remove 'fake' and 'ssh' drivers from default enabled list

Remove the 'fake' and 'ssh' drivers, since they should not show up in
production, and it is better to have production-oriented sane defaults.

Updates the option doc string with a lengthy description.

Updates the developer documentation with a link to the wiki page,
where a list of CI-tested drivers will be maintained.

Change-Id: I1151ace22752efdf6a8a43e279a57d728ea6cce2
Add node id to DEBUG messages in impitool

Change-Id: Ic421350c4c5f8278ac020ee6a521026960e88634
Closes-Bug: #1319637
Merge "Remove 'fake' and 'ssh' drivers from default enabled list"
Merge "Add node id to DEBUG messages in impitool"