target/configfs: handle match_int() errors

As a follow up to ce31c1b0 - there are
still a few LIO match_int() calls that don't check the return value.
Propagate errors rather than using the potentially uninitialised result.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>