When volumes.enable flag is off in Docker driver, disable all mounts of
paths outside alloc dir.

consul: add ScriptExecutor context wrapper

consul: fix script checks exiting after 1 run

executor: kill all container processes

Recover from any possible io error when invoking Write on FileRotator

Don't GC running but desired stop allocations

As of now, FileRotator uses bufio.Write under the hood to write data to
configured output file. Due to the way how bufio handles any occurred io
error - saves it into `err` variable never resetting it automatically -
any operation like `Write`, `Flush` etc will become a no-op, returning the very same,
saved error (eg. Out of disk space) even when the problem is fixed (eg. disk
space is available again).

That automatically means that FileRotator will stop writing any logs,
reporting the same error over and over again, even if it's no longer
valid.

This PR fixes it by resetting the bufio Writer, which resets any errors
and tries to write requested data.

Mount Devices in container based drivers

Re-enable Client GC tests

Fix docker driver tests

deviceDir is used for specifying mount/device host paths, and those
should be absolute paths.

Also, LXC requires target paths to be relative.  Container paths in LXC
binds should never be absolute paths, so we strip any preceeding `/`,
even if a user sets one.

UI: Keep line charts in their canvases at all times

The previous integration test was broken during the client refactor, and
it seems to be some sort of race with state updating.

I'm going to try and construct a replacement test as part of work on
performance, but for now, the underlying behaviour is still being
tested.

Fix various bugs with task events

Fixes the following:
* Emitting events when the task fails to start
* Don't double emit events on task shutdown (nomad stop)
* Don't emit a OOM kill metric unless actually OOM'd

This PR fixes an edge case where we could GC an allocation that was in a
desired stop state but had not terminated yet. This can be hit if the
client hasn't shutdown the allocation yet or if the allocation is still
shutting down (long kill_timeout).

Fixes https://github.com/hashicorp/nomad/issues/4940

Simplify the tests to do all assertions within the main goroutine and
account for status propagation delay.

server/vault: Lock Vault expiration tracking

tests: fix rkt tests

0.8.6 uses exit code 1 when `proc.Wait()` fails: https://github.com/hashicorp/nomad/blob/v0.8.6/client/driver/executor/executor.go#L442

The rkt command itself needs an environment with PATH set to find iptables.

Add guards around subtracting summary count

Also update the new recommended `nomad job` subcommands

* Add Nomad RA

* Add deployment guide and nav

* Deployment Guide update

* Minor typo fixes

* Update diagrams

* Fixes for review

* Link fixes and typo fix

* Edits following review

- Update image text from "zone" to "datacenter" to match Nomad terminology
- Clean up text based on Preetha's feedback

* Text updates

Based on feedback from Rob

* Update diagrams

* fixing spelling

* Add suggestions from Preetha and Omar

WaitForResult expects body to fail and retries few times before giving
up.  Assertions inside the testfn body causes it to terminate abruptly
without retrying.