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

Use `/tmp` as temporary directory for docker driver tests, so tests can
run out of the box without any intervention.

macOS sets tempdir as `/var`, which Docker does not whitelist as a path
that can be bind-mounted.

drivers/exec: restrict devices exposed to tasks

Allow scheduling mock job when running on MacOS (or Windows) hosts.

The whole approach to monitoring drains has ordering issues and lacks
state to output useful error messages.

AFAICT to get the tests passing reliably I needed to change the behavior
of monitoring.

Parts of these tests are skipped in CI, and they should be rewritten as
e2e tests.

Emit Killing task events and add e2e tests

Error expects an odd number of arguments, and panics otherwise.

This fixes a bug related to shutting down of GRPC plugin interfaces
(more info: https://github.com/hashicorp/go-plugin/pull/88)

This does not yet fix all test cases for subprocess leaking, but is a
useful independant change.

test: re-eanble periodic fingerprint test

We were just emitting Killed/Terminated events before. In v0.8 we
emitted Killing/Killed, but lacked Terminated when explicitly stopping
a task. This change makes it so Terminated is always included, whether
explicitly stopping a task or it exiting on its own.

New output:

2019-01-04T14:58:51-08:00  Killed            Task successfully killed
2019-01-04T14:58:51-08:00  Terminated        Exit Code: 130, Signal: 2
2019-01-04T14:58:51-08:00  Killing           Sent interrupt
2019-01-04T14:58:51-08:00  Leader Task Dead  Leader Task in Group dead
2019-01-04T14:58:49-08:00  Started           Task started by client
2019-01-04T14:58:49-08:00  Task Setup        Building Task Directory
2019-01-04T14:58:49-08:00  Received          Task received by client

Old (v0.8.6) output:

2019-01-04T22:14:54Z  Killed            Task successfully killed
2019-01-04T22:14:54Z  Killing           Sent interrupt. Waiting 5s before force killing
2019-01-04T22:14:54Z  Leader Task Dead  Leader Task in Group dead
2019-01-04T22:14:53Z  Started           Task started by client
2019-01-04T22:14:53Z  Task Setup        Building Task Directory
2019-01-04T22:14:53Z  Received          Task received by client

tests appropriately

Test fix races