s4:samba_spnupdate: do not attempt to parse log level, use parsed value

s4:samba_spnupdate: do not attempt to parse log level, use parsed value

The log level parameter can contain debug class specific entries.
Do not attempt to parse this as int, but use the values that the
debugging system already parsed

BUG: https://bugzilla.samba.org/show_bug.cgi?id=9945
Signed-off-by: Christian Ambach <ambi@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Christian Ambach <ambi@samba.org>
Autobuild-Date(master): Wed Sep 14 23:15:18 CEST 2016 on sn-devel-144