This PR fixes various instances of plugins being launched without using
the parent loggers. This meant that logs would not all go to the same
output, break formatting etc.

Re-enable client and java skipped tests

Remove unnecessary usage of alloc.Resource

Docs for spread stanza

Oxford comma in variable interpolation summary

This improves the readability of this section.

WaitForRunning risks a race condition where the allocation succeeds and
completes before WaitForRunning is called (or while it is running).

Here, I made the behavior match the function documentation.

I considered making it stricter, but callers need to account for
allocation terminating immediately after WaitForRunning terminates
anyway.

tests: remove tests for unsupported features

With switching to driver plugins, driver validation is quite tricky and
we need to do some design thinking before supporting it against.

ignore _JAVA_OPTIONS line in `java -version`, as it's relevant.

added validation on client metadata keys

Improve Kill handling on task runner

Co-Authored-By: dadgar <alex@hashicorp.com>

drain: fix node drain monitoring

tests: run docker tests in macOS out of box

Extract LXC from nomad

drivers: avoid referencing client/structs package

Add another task events e2e test and fix test helper

Fix a panic on node.Deregister fail

Fix Travis MacOS job 

This PR improves how killing a task is handled. Before the kill function
directly orchestrated the killing and was only valid while the task was
running. The new behavior is to mark the desired state and wait for the
task runner to converge to that state.

node.NodeResources is nil when operating against pre-0.9.

vendor: Update go-plugin

Before it was *exactly* N nodes which limited test portability between
clusters.

validation in the future

config dir clarification