tdb: Fix build on AIX

tdb: Fix build on AIX

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13493

Here is the build error on AIX 7.1.

../../lib/tdb/tools/tdbtool.c:39:12: error: 'disable_lock' redeclared as different kind of symbol
 static int disable_lock;
            ^~~~~~~~~~~~
In file included from /usr/include/sys/gfs.h:24:0,
                 from /usr/include/sys/vfs.h:27,
                 from ../../lib/replace/system/filesys.h:48,
                 from ../../lib/tdb/tools/tdbtool.c:26:
/usr/include/sys/lock_def.h:314:5: note: previous declaration of 'disable_lock' was here
 int disable_lock(int,simple_lock_t);
     ^~~~~~~~~~~~

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>