onie-discovery-stop does not kill the entire discovery process immediately

[cbrune]

The onie-discovery-stop command is not thorough enough. In some circumstances the eth0 network configuration step lingers longer than desired after issuing onie-discovery-stop.

See the mailing list for more:
http://lists.opencompute.org/pipermail/opencompute-onie/2017-August/001497.html