s4:torture:dlz_bind9: fix spnego tests

s4:torture:dlz_bind9: fix spnego tests

The dlz_bind9 module uses the special dns-${NETBIOSNAME} account,
and this is only available under the dns/hostname.domain SPN, not
host/hostname.

Also the dlz_ssumatch() function returns isc_boolean_t instead
of isc_result_t. As ISC_R_SUCCESS and ISC_FALSE have the same value
we didn't notice this problem.

Change-Id: I48539c3f48f5dde9eaa2fff6da0f3be2f9f66311
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>