Initialize nscd stats data [BZ #17892]

The padding bytes in the statsdata struct are not initialized, due to
which valgrind throws a warning:

==11384== Memcheck, a memory error detector
==11384== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==11384== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==11384== Command: nscd -d
==11384==
Fri 25 Apr 2014 10:34:53 AM CEST - 11384: handle_request: request received (Version = 2) from PID 11396
Fri 25 Apr 2014 10:34:53 AM CEST - 11384:       GETSTAT
==11384== Thread 6:
==11384== Syscall param socketcall.sendto(msg) points to uninitialised byte(s)
==11384==    at 0x4E4ACDC: send (in /lib64/libpthread-2.12.so)
==11384==    by 0x11AF6B: send_stats (in /usr/sbin/nscd)
==11384==    by 0x112F75: nscd_run_worker (in /usr/sbin/nscd)
==11384==    by 0x4E439D0: start_thread (in /lib64/libpthread-2.12.so)
==11384==    by 0x599AB6C: clone (in /lib64/libc-2.12.so)
==11384==  Address 0x15708395 is on thread 6's stack

Fix the warning by initializing the structure.