IpmiDcmi: find ipmi-dcmi in path, if available
IpmiDcmi: find ipmi-dcmi in path, if available

The path to ipmi-dcmi was hardcoded, because not everything keeps
/usr/sbin in path. That hardcoding remains, but is only used if
ipmi-dcmi can't be found in $PATH.

Cynerva/pyipmi,emaadmanzoor/pyipmi