ctdb-scripts: Add systemd services to NFS call-out

ctdb-scripts: Add systemd services to NFS call-out

At least Red Hat and Debian appear to use (a variant of?) the upstream
systemd units for NFS, so adding support for these services is
relatively easy.  Distributions using Sys-V init can patch the
call-out to use the relevant Sys-V init services.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13860

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@samba.org>
(cherry picked from commit a8fafd377ff0cb07ab161e437c5fe024704345eb)