Update CTDB and NFS scripts for new nfs server layout

nfs-utils 2.6.1 is now in unstable and testing, and it changes a bit the layout of the services and configuration files. Most notably, /etc/default/nfs-* are no longer used by the daemons and were replaced by a single /etc/nfs.conf ini-style file.

This PR changes the ctdb and supporting nfs scripts to handle this new layout. It also changes the example nfs scripts and config files provided in the ctdb examples directory to work with this new layout.

I haven't submitted the ctdb changes upstream, because upstream has to handle all sorts of Linux distributions in a generic way, but if you think this is a requirement, I could give it a try, but it may take a while. It's a complicated chain of shell scripts being called by other scripts responding to events.

The "XXX" comments in the nfs_rquotad_services I discussed a bit with upstream at https://lists.samba.org/archive/samba/2022-March/240108.html, and that resulted in some upstream changes, but is still not a super ideal situation. In any case, I think clustering is hard to appease every possible deployment scenario, and I think we have a good compromise.

I kept many commits separate, specially one that renames files, to make it easier to review each change.