ctdb-doc: Add example for NFS-Ganesha RPC checking

ctdb-doc: Add example for NFS-Ganesha RPC checking

This one does an rpcinfo check, along with statistics mitigation.  It
can be used in combination with the existing 20.nfs_ganesha.check.

The equivalent kernel NFS file only restarts every 10 failures.  This
one can be a little more proactive given that false positives are less
likely with the statistics mitigation.

Signed-off-by: Martin Schwenke <mschwenke@ddn.com>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>