Add ironic-python-agent deploy driver

This commit adds a deploy driver for the ironic-python-agent
project. Caveats:

* Only basic functionality (deploy and tear_down) is implemented.
* Only whole disk images are supported.

Implements: blueprint agent-driver

Change-Id: Iebf8d8f756770549d6fcd1bb2fe94d2585d576b1
Merge "Add ironic-python-agent deploy driver"