packaging: Make the ostree rpm own and create /etc/ostree/remotes.d/

We need the rpm to create this directory in order to avoid errors like the ones below:

-bash-4.2# ostree remote add --set=gpg-verify=false dustyserver http://192.168.122.124:8000/           
error: Error opening file '/etc/ostree/remotes.d/dustyserver.conf': No such file or directory