Change nova compute driver location

This patch changes the location of the Ironic Nova compute driver
in nova.conf so that it uses the driver from within the Ironic
directory tree. This patch will need to be reverted once the Ironic Nova
driver lands in the nova.

Change-Id: I9199d506f3665cb0827edd642a1806713a42b90e
Merge "Change nova compute driver location"