Fix minor typo in IPMI virt driver

The correct driver to use is:
    nova.virt.baremetal.ipmi.IPMI
instead of:
    nova.virt.baremetal.ipmi.Ipmi

Change-Id: I2bf11a3acb72f7c2ba37f1a03efe09f50dc9d239
diff --git a/lib/baremetal b/lib/baremetal
index 2659386..ecbe0c0 100644
--- a/lib/baremetal
+++ b/lib/baremetal
@@ -63,7 +63,7 @@
 
 # sub-driver to use for remote power management
 # - nova.virt.baremetal.fake.FakePowerManager, for manual power control
-# - nova.virt.baremetal.ipmi.Ipmi, for remote IPMI
+# - nova.virt.baremetal.ipmi.IPMI, for remote IPMI
 # - nova.virt.baremetal.tilera_pdu.Pdu, for TilePro hardware
 BM_POWER_MANAGER=${BM_POWER_MANAGER:-nova.virt.baremetal.fake.FakePowerManager}