Get rid of need for host uuid

[Eric Fried]

We don't need host uuid for things like scsi mapper. We have to leave it in the signature for legacy reasons, but I could surely make it so you can just pass None.

[Eric Fried (efried)]

This is ongoing, but extremely low priority.

[Eric Fried (efried)]

Next up:
- Cache the sys UUID in the Adapter so we can use it from wherever without having to GET the ManagedSystem
- Identify all wrappers representing CHILDren of ManagedSystem and override their .get (and possibly other) methods to use ^ and therefore not need the parent_* kwargs
- Get rid of said kwargs in all references to said wrappers (here and in consuming code).

[Eric Berglund (esberglu)]

Some of the work was done in these commits. There may be more to do, I'm not sure since it's been so long since I've looked at this. Marking unassigned since I'm no longer on the team.

https://github.com/powervm/pypowervm/commit/2999b8128f85df3c969751c1e4a71dc3af741d2e
https://github.com/powervm/pypowervm/commit/651a01b630650083db78511b9297977a3fbe4876
https://github.com/powervm/pypowervm/commit/346d0c0df98b203fd0ee1ab4d0da14dff03225ce