Fix ironic compute_driver name

This commit fixes breaking change [0].
Long driver names like 'nova.virt.libvirt.libvirtDriver' are
no longer available and 'libvirt.libvirtDriver' should be used
instead.

Reference:
[0] https://review.openstack.org/309504

Change-Id: I27a1b75b921c7401bc8614caadfd1e09e7dd5d65
Closes-Bug: 1574990
diff --git a/lib/nova_plugins/hypervisor-ironic b/lib/nova_plugins/hypervisor-ironic
index 43e7797..c40427c 100644
--- a/lib/nova_plugins/hypervisor-ironic
+++ b/lib/nova_plugins/hypervisor-ironic
@@ -39,7 +39,7 @@
     configure_libvirt
     LIBVIRT_FIREWALL_DRIVER=${LIBVIRT_FIREWALL_DRIVER:-"nova.virt.firewall.NoopFirewallDriver"}
 
-    iniset $NOVA_CONF DEFAULT compute_driver nova.virt.ironic.IronicDriver
+    iniset $NOVA_CONF DEFAULT compute_driver ironic.IronicDriver
     iniset $NOVA_CONF DEFAULT firewall_driver $LIBVIRT_FIREWALL_DRIVER
     iniset $NOVA_CONF DEFAULT scheduler_host_manager ironic_host_manager
     iniset $NOVA_CONF DEFAULT ram_allocation_ratio 1.0