Description of problem:
When the owfs-fs package is updated, changes made to /usr/lib/systemd/system/owfs.service are lost. This is because the config files are not appropriately declared in the spec file.
Modified config files are preserved as per normal RPM behaviour.
Suggest to add following line, or similar, to %files section of spec file:
Files in /usr are not config files, and they are supposed to be overwritten on upgrade. If you need to modify unit file, copy it to /etc/systemd/system or use snippets mechanism.