I propose the same patch with a modification to work with spaces in the path, since systemctl prints spaces as '\x20', so we just needed one more sed to replace that with a space.
Would also like to see this fixed in the next minor release, since it makes it really hard to change PGDATA the correct way, which is by droping a .conf file into /etc/systemd/system/postgresql-9.x.service.d/ directory.
Also would be really cool if the postgres rpm created the /etc/systemd/system/postgresql-9.x.service.d/ directory, but it's not that important as the setup scripts working correctly.