lib:util: Fix DEBUGCLASS pointer initializiation

lib:util: Fix DEBUGCLASS pointer initializiation

This fixes a segfault in pyglue:

==10142== Process terminating with default action of signal 11 (SIGSEGV)
==10142==  Bad permissions for mapped region at address 0x6F00A20
==10142==    at 0x6F1074B: py_set_debug_level (pyglue.c:165)

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13679

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 71ef09c1afdbf967b829cb66b33c3a5cb1c18ba0)

Autobuild-User(v4-8-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-8-test): Mon Nov 12 18:01:17 CET 2018 on sn-devel-144