Generic handling of server region errors

test: don't rely on alloc runner update count

Fix issue where force deadlines weren't respected

We were incorrectly relying on the count of alloc updates in a number of
tests. Since alloc updates are async, their number is non-determinstic
and largely meaningless.

This should fix quite a few flaky tests in Travis and prevent future
mistaken assumptions in tests.

Unset drain when final batch allocs finish

docs: clarify service.port depends on address_mode

add HasHealth helper for nil checks

This PR handles upgrading a node that has no scheduling eligiblity set.

handle missing finishedAt

UI: Service job breadcrumbs + errant open connections

It was possible for a url to be overridden then canceled, leaving the
open connection open and forgotten about.

Add node events to documentation

Filter desired status stop allocs correctly 

drain: block cli until all allocs stop

This PR allows aliased commands to be autocompleted but still filters
them from the help output.

UI: Upgrade Ember to LTS + fix job summary issues

UI: Check for a case-sensitive or lowercase header value