Fixed rpmlint warnings
Fixed rpmlint warnings

- Use %{_unitdir} instead of hardcoded /usr/lib/systemd/system
- Added "BuildRequires: systemd" as required by %{_unitdir}
- Use standard group "System Environment/Daemons"
- Do not use $RPM_BUILD_ROOT before installation phase (%prep)
- *.service files must not be %config files

Ref: https://fedoraproject.org/wiki/Packaging:Systemd#Filesystem_locations
Ref: https://fedoraproject.org/wiki/Packaging:Systemd#.25files_section

fmidev/smartmet-server,fmidev/smartmet-server