ctdb-scripts: Add a 'rm' stub so statd-callout tests work correctly

ctdb-scripts: Add a 'rm' stub so statd-callout tests work correctly

statd-callout tries to remove global files from /var/lib/nfs/statd and
this causes errors in tests.  Add an rm stub that ignores attempts to
remove these files but invokes /bin/rm for anything else.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Pair-programmed-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Martin Schwenke <martin@meltin.net>
(cherry picked from commit 956e51707d7ddcff060352f54d11ff42bdcc51ef)

The last 10 patches address

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11204

CTDB statd-callout does not scale.