Extended checking whether system service exists

- Sometimes there's no service in systemd directories
  so I had to re-enable also fallback checking in
  /etc/init.d directory
Changes file and a new version
Constants are usually upper-cased
Merge pull request #42 from kobliha/master

Extended checking for service in Service module by also checking in /etc/init.d as a fallback (bnc#795929 comment#20).