nfsdcltrack: rename the nfsdcld directory and options to nfsdcltrack

We'll soon be adding a new nfsdcltrack program, at which point it won't
make much sense to call this directory and the config option "nfsdcld".
Rename it to be a bit more generic.

While we're at it, change the default for --enable-cltrack to "yes".
When we introduce the one-shot program, we're going to want to build
it by default anyway.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>