Bug 1162422 - <oo-install> crash on move node

- Fix oo-install crash when moving a node between districts
yum-validator: add retry/timeout to subscription-manager subprocess calls

`subscription-manager` can fail for repo-override commands due to HTTP
errors when contacting the remote candlepin server. This change adds a
retry with expanding timeout for `subscription-manager` calls to try
to account for these failures.
<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 #492 from detiber/bz1162422

Bug 1162422 - <oo-install> crash on move node
Bug 1163036 - <oo-install> fix crash when moving districts

https://bugzilla.redhat.com/show_bug.cgi?id=1163036

- previously if only one district was defined and you tried to move
  the host district, the installer would crash.
Merge pull request #496 from detiber/bz1163036

Bug 1163036 - <oo-install> fix crash when moving districts
Merge pull request #495 from detiber/bz1163338

Bz1163338 <oo-install> - Improve command detection and error handling
Merge pull request #502 from dobbymoodge/handle_rhsm_errors

yum-validator: add retry/timeout to subscription-manager subprocess calls

I've tested this already, and need to cherry-pick it downstream