Update opensource cmdpath

The opensource gem uses /usr/bin for the cmdpath.  'createkey' does not work with the current deafult path, and leads to this error:

Error: Could not find command '/usr/bin/puppet/eyaml'
Error: /Stage[main]/Hiera::Eyaml/Exec[createkeys]/returns: change from notrun to 0 failed: Could not find command '/usr/bin/puppet/eyaml'