s4/torture: fix timeval wrap in torture_libsmbclient_utimes() test

s4/torture: fix timeval wrap in torture_libsmbclient_utimes() test

Fixes the following flapping test:

UNEXPECTED(failure): samba4.libsmbclient.utimes.SMB3.utimes(nt4_dc)
REASON: Exception: Exception: ../../source4/torture/libsmbclient/libsmbclient.c:1249:
    st.st_mtim.tv_nsec / 1000 was 98181 (0x17F85),
    expected 1098181 (0x10C1C5): smbc_utimes did not update msec

https://gitlab.com/samba-team/devel/samba/-/jobs/506361470

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Sat Apr 11 12:24:00 UTC 2020 on sn-devel-184