<oo-install> always set conf_node_external_eth_dev for origin
Bug 1163338 - Improve command detection and error handling

https://bugzilla.redhat.com/show_bug.cgi?id=1163338

- explicity search /sbin and /usr/sbin when looking for utilities
- improve error handling around confirm_access
Merge pull request #495 from detiber/bz1163338

Bz1163338 <oo-install> - Improve command detection and error handling