Revert commit b2c18ec1dfb32fb339b0d32afc5aa7832552d515

The original patch works fine to avoid cancelling a job when all
of it's nodes go unresponsive, but I don't see any way to easily
address nodes coming back into service. We want to cancel jobs
that have some up nodes and some down nodes, but the nodes will
come back into service indivually rather than all at once.