Fixed logging prefixes after moving state/api -> api/ and state/apiserver -> apiserver/

After https://github.com/juju/juju/pull/655 got merged, I noticed some loggers are still using "state.api.*" and "state.apiserver.*", so this fixes these to drop the "state." prefix.

Also, added more logging to juju/testing/conn.go and state.Close() hoping to provide more context for fixing CI bugs like http://pad.lv/1348477.