Add status option to Debian init script

[Chef](http://opscode.com) and presumably other programs rely on a init.d 'status' option to reliably determine if a service is running. (Chef, in particular, 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, 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.