Fix supervisorctl command when no process is present

[jsok]

Currently, if you try to create an instance like

supervisord::supervisorctl { 'restart_myapp':
  command => 'command',
}

You end up with an exec command like /usr/local/bin/supervisorctlcommand.

This branch adds the require missing space and increase test coverage over the type.

[ajcrowe]

Thanks for this fix @jsok not sure how that slipped through!