Add /sbin to the net-info job builder path

* .../files/jenkins_job_builder/config/macros.yaml(net-info): Most
distributions place iproute2's ip command in /sbin but Jenkins seems
to remove this from the default path, so add it.

Change-Id: I618c473d9cafed3c209183d32f4ae5efb8edddda
Merge "Add /sbin to the net-info job builder path"