Fix a deadlock relating to blocked allocations

dont throw away errors in log rotation

Update API documentation

Update consul/api

Add new gc_max_allocs tuneable

Since I was already fixing consul's tls handling in #2645 I decided to
update consul/api and pre-emptively fix our tls handling against the
newest consul/api behavior. consul/api's handling of http.Transports has
improved but would have broken how we handled tls (again).

This would have made for a nasty surprise the next time we updated
consul/api.

Add envconsul-like support and refactor environment handling

Don't advertise sockaddr support just yet; focus on the saner advertise default

Don't autoadvertise private ip if bind=localhost

A slight improvement to #2399 - if bind is localhost, return an error
instead of advertising a private ip. The advertised ip isn't valid and
will just cause errors on use. It's better to fail with an error message
instructing users how to fix the problem.