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
Merge "Fix minor typo in IPMI virt driver"