selftests: icmp_redirect: pass xfail=0 to log_test()

If any sub-test in this icmp_redirect.sh is failing but not expected
to fail. The script will complain:
    ./icmp_redirect.sh: line 72: [: 1: unary operator expected

This is because when the sub-test is not expected to fail, we won't
pass any value for the xfail local variable in log_test() and thus
it's empty. Fix this by passing 0 as the 4th variable to log_test()
for non-xfail cases.

v2: added fixes tag

Fixes: 0a36a75c ("selftests: icmp_redirect: support expected failures")
Signed-off-by: NPo-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/net/icmp_redirect.sh

@@ -311,7 +311,7 @@ check_exception()
 		ip -netns h1 ro get ${H1_VRF_ARG} ${H2_N2_IP} | \
 		grep -E -v 'mtu|redirected' | grep -q "cache"
 	fi
-	log_test $? 0 "IPv4: ${desc}"
+	log_test $? 0 "IPv4: ${desc}" 0
 
 	# No PMTU info for test "redirect" and "mtu exception plus redirect"
 	if [ "$with_redirect" = "yes" ] && [ "$desc" != "redirect exception plus mtu" ]; then