ref(controller): remove close_db_connection tests hack

The decorator once allowed us to work around issues with running
our test suite, but does not seem to be needed now.
fix(contrib/coreos): bump etcd peer heartbeat to 500ms
Merge pull request #1831 from carmstrong/etcd_500

fix(contrib/coreos): bump etcd peer heartbeat to 500ms
fix(scheduler): handle announcer timeouts to work around https://github.com/docker/docker/issues/8022
Merge pull request #1832 from gabrtv/announcer-timeout

fix(scheduler): handle announcer timeouts explicitly
Merge pull request #1830 from mboersma/remove-close-db-hack

ref(controller): remove close_db_connection tests hack