Make validate command ignore environment variables in service name

Don't emit metrics for non-running tasks

Change error message to use original name for clarity, rather than the name after substituting env vars with placeholder.

Remove rkt pods when exiting

Fix Docker name conflict bug by updating dockerclient

Fixes #3561

Dropped loglevel for AWS fingerprinter env read misses to DEBUG

Better interface selection heuristic

Handle leader task being dead in RestoreState

Fixes the panic mentioned in
https://github.com/hashicorp/nomad/issues/3420#issuecomment-341666932

While a leader task dying serially stops all follower tasks, the
synchronizing of state is asynchrnous. Nomad can shutdown before all
follower tasks have updated their state to dead thus saving the state
necessary to hit this panic: *have a non-terminal alloc with a dead
leader.*

The actual fix is a simple nil check to not assume non-terminal allocs
leader's have a TaskRunner.

Certain environments use WARN for serious logging; however, it's very
possible to have machines without some of the fingerprinted keys
(public-ipv4 and public-hostname specifcally).  Setting log level to
INFO seems more consistent with this possibility.

Handle edge case when allocation create/modify time difference is les…

* Allow server TLS configuration to be reloaded via SIGHUP

* dynamic tls reloading for nomad agents

* code cleanup and refactoring

* ensure keyloader is initialized, add comments

* allow downgrading from TLS

* initalize keyloader if necessary

* integration test for tls reload

* fix up test to assert success on reloaded TLS configuration

* failure in loading a new TLS config should remain at current

Reload only the config if agent is already using TLS

* reload agent configuration before specific server/client

lock keyloader before loading/caching a new certificate

* introduce a get-or-set method for keyloader

* fixups from code review

* fix up linting errors

* fixups from code review

* add lock for config updates; improve copy of tls config

* GetCertificate only reloads certificates dynamically for the server

* config updates/copies should be on agent

* improve http integration test

* simplify...

Includes this workaround:
https://github.com/fsouza/go-dockerclient/blob/99ba9a9ff48803e4bf801b025c6be7707d83c421/container.go#L634-L637

Fails on Docker 17.09, passes on Docker 17.06 and earlier