The old logic for cancelling duplicate blocked evaluations by job id had
the issue where the newer evaluation could have additional node classes
that it is (in)eligible for that we would not capture. This could make
it such that cluster state could change such that the job would make
progress but no evaluation was unblocked.
This PR causes blocked evaluations to be cancelled if there is a
subsequent successful evaluation for the job. This fixes UX problems
showing failed placements when there are not any in reality and makes GC
possible for these jobs in certain cases.
Fixes https://github.com/hashicorp/nomad/issues/2124
Alex Dadgar