Updates compute node compute_driver opt
Updates compute node compute_driver opt

Changes Hyper-v compute node's nova.conf compute_driver option from nova.virt.hyperv.driver.HyperVDriver to hyperv.driverHyperVDriver.

Recent changes in nova made it so out-of-tree drivers cannot be imported. Because of this, the current config option value is no longer valid.

This change should also work on stable branches.
rbuzatu90/neutron-ci,rbuzatu90/neutron-ci,cloudbase/neutron-ci,costingalan/neutron-ci,costingalan/neutron-ci,cloudbase/neutron-ci