Change nova scheduler driver location

This patch changes the location of the Ironic Nova scheduler 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 scheduler driver lands in the nova.

Change-Id: I1222b363f86fafb9ac739466a74bb90975f49702
Merge "Change nova scheduler driver location"