ctdb: add ctdb_wrapper as a wrapper to call ctdb from the cmdline

ctdb: add ctdb_wrapper as a wrapper to call ctdb from the cmdline

This is useful for non-standard installations since
it reads the socket from the config file so the user
does not need to specify it. Just a convenience tool
which removes the need to set environment variables
prior to calling ctdb.

This is similar to ctdbd_wrapper for ctdbd but
much more simple.

Signed-off-by: Michael Adam <obnox@samba.org>