ctdb-build: Specify absolute path to libsocket-wrapper.so

ctdb-build: Specify absolute path to libsocket-wrapper.so

Specifying a relative path to LD_PRELOAD can fail if any of the test
scripts uses cd to change directory and execute commands.

Adding statd-callout tests breaks autotest since statd-callout does "cd".

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

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Wed Mar  4 13:11:53 CET 2015 on sn-devel-104
(cherry picked from commit 7a10e077706efd3b5d2ce024084b7ed97d4cd36c)