Add durable HostID generation support to Windows.

https://github.com/shirou/gopsutil/pull/312

Merging GC related config values

Reproducible Node ID

Fix Consul Config Merging/Copying

Vendor Serf and Memberlist

Template destination file permissions.

Vault Client on Server handles SIGHUP

Prep for 0.5.5 and add changelog entry for #2266

Fix race condition with Deriving vault tokens

This PR fixes config merging/copying code.

Fixes https://github.com/hashicorp/nomad/issues/2264

Checking in updated gc tests

This PR fixes a race condition in which the client was not locked while
deriving Vault tokens. This allowed the token to be set which would
cause subsequent Vault requests to fail with permission denied because
the incorrect Vault token was being used.

Further this PR makes the unsetting and unlocking of the client atomic
to avoid an even harder to hit race condition (not sure it was ever hit
but was still incorrect).

Expand rkt port_map docs since it confused me

(and I wrote it)

Fixes #2272