This change deflakes timeout, deadline tests, especially fixes socket
and goroutine leaks. Also adds a few missing tests that use features
introduced after go1 release.

Change-Id: Ibf73a4859f8d4a0ee494ca2fd180cbce72a7a2c7
Reviewed-on: https://go-review.googlesource.com/9464Reviewed-by: Ian Lance Taylor <iant@golang.org>