Add status option to Debian init script

[Chef](http://opscode.com) needs an init script 'status' option to reliably determine if a service is running. It otherwise falls back to highly unreliable process table inspection. This commit adds that option, using the Debian-standard `status_of_proc` shell function.

Please note that Ubuntu 12.04 isn't [LSB-compliant](http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html) (argh), so `sudo service opentsdb status` will return exit code 4 (unknown service status) if the service is not running. This was fixed in 12.04.2 and up—see [original Debian bug](http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=664621) if you're interested.