Docs: Update UI API and UI Guide

Fix flaky api/jobs tests based on index != 0

 drain: fix double-close panic on drain future

fix flaky pretty time test

Improve handling of Vault errors

Fix flaky deadline tests

If one error is encountered it is unlikely any further attempts will
succeed, so fail fast.

Support custom Consul config for TestServer

Adds a Consul field to the TestServerConfig that allows passing in non-default values for e.g. consul address.
This will allow the TestServer to integrate with Consul's testutil/TestServer.

Correctly handle the upgrade path of a node being drained when applying Raft logs

This is no longer true 

* transistion -> transition
* don't t.Fatal in goroutines
* don't mutate global state

aka What If structs.go Wasn't So Big?

Add name variable to AWS Terraform configs

Initial Node drain docs

Check for nil for RPC listener; prevent double closing of listener channel