Fixes a bug in the AllocatedResources.Comparable method, where the scheduler
would only take into account the cpusets of the tasks in the largest lifecycle.
This could result in overlapping cgroup cpusets. Now we make the distinction
between reserved and fungible resources throughout the lifespan of the alloc.
In addition, added logging in case of future regressions thus not requiring
manual inspection of cgroup files.
* client: refactor cpuset partitioning
This PR updates the way Nomad client manages the split between tasks
that make use of resources.cpus vs. resources.cores.
Previously, each task was explicitly assigned which CPU cores they were
able to run on. Every time a task was started or destroyed, all other
tasks' cpusets would need to be updated. This was inefficient and would
crush the Linux kernel when a client would try to run ~400 or so tasks.
Now, we make use of cgroup heirarchy and cpuset inheritence to efficiently
manage cpusets.
* cr: tweaks for feedback
