Add ssh power manager.

Converting nova's virtual_power_manager for use by ironic

Implements: blueprint virtual-power-driver.

Change-Id: Ie24564e349aca863578955385f084f1be8b0b053
Authored-by: Devananda van der Veen <devananda.vdv@gmail.com>
Authored-by: Chris Krelle <nobodycam@gmail.com>
Merge "Add ssh power manager."