Fixes start_program/stop_program being malformed

3fcbfa5 introduced bug whereby service_bin, script_name, start_cmd and
stop_cmd must be explicitly specified by the resource.

This commit requires a resource to specify a script_name otherwise
start_program and stop_program supplied to the template are "".

Issue https://github.com/rcbops/chef-cookbooks/issues/972
Issue https://github.com/rcbops/chef-cookbooks/issues/860
Merge pull request #46 from git-harry/hfc423

Fixes start_program/stop_program being malformed