Virtual power driver is superceded by ssh driver

Equivalent functionality was added in ironic/drivers/modules/ssh.py
previously, in commit Ie24564e349aca863578955385f084f1be8b0b053,
but the corresponding nova files were not removed. This patch simply
removes these unneeded files.

Change-Id: I529f1dc7db677b1db99798f8849e9f92a070d5f2
Remove unused APICoverage class

This is used in Nova to ensure that VirtAPI has a test per method in the
class. We're not using it in Ironic now, so let's remove it.

Change-Id: I382e7d6da0946e0036add161f74d7faaf482bbbc
Merge "Remove unused APICoverage class"
Merge "Virtual power driver is superceded by ssh driver"