Rename ipmi driver to ipmitool

To make naming more consistent with other ipmi drivers that
will be introduced later, the module name for ipmi driver
that uses the ipmitool is renamed from ipmi to ipmitool.

Change-Id: I8ec0d4beb29a06af7b27d3ff0620fab5446579b1
Merge "Rename ipmi driver to ipmitool"