Extends the BasicAllocStats test to include a test for Windows
clients, exercising stats via a powershell `raw_exec` job.
Adds `ListLinuxClientNodes` and `ListWindowsClientNodes` utils so that
we can scope tests to run only when Linux or Windows clients are
available. This prevents waiting on timeouts when running a subset of
the tests against a development cluster (vs our nightly test
cluster).
- In script checks, ensure we're running `Exec` against the new running
allocation and not the earlier stopped one.
- In script checks, allow `Exec` calls to error due to lack of pty when
we use the exec to kill the task.
- In `utils.go/RegisterAllocs`, force query for allocations to wait on
wait index returned by registration call.
The e2e test code is absolutely hideous and leaks processes and files
on disk. NomadAgent seems useful, but the clientstate e2e tests are very
messy and slow. The last test "Corrupt" is probably the most useful as
it explicitly corrupts the state file whereas the other tests attempt to
reproduce steps thought to cause corruption in earlier releases of
Nomad.
