selftests: forwarding: tc_flower: Relax success criterion

The test checks that filters that match on source or destination MAC
were only hit once. A host can send more than one packet with a given
source or destination MAC, resulting in failures.

Fix by relaxing the success criterion and instead check that the filters
were not hit zero times. Using tc_check_at_least_x_packets() is also an
option, but it is not available in older kernels.

Fixes: 07e5c75184a1 ("selftests: forwarding: Introduce tc flower matching tests")
Reported-by: Mirsad Todorovac <[e-mail]>
Closes: https://lore.kernel.org/netdev/[e-mail]/
Signed-off-by: Ido Schimmel <[e-mail]>
Reviewed-by: Petr Machata <[e-mail]>
Tested-by: Mirsad Todorovac <[e-mail]>
Reviewed-by: Hangbin Liu <[e-mail]>
Acked-by: Nikolay Aleksandrov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/forwarding/tc_flower.sh

···
 	tc_check_packets "dev $h2 ingress" 101 1
 	check_fail $? "Matched on a wrong filter"
 
-	tc_check_packets "dev $h2 ingress" 102 1
-	check_err $? "Did not match on correct filter"
+	tc_check_packets "dev $h2 ingress" 102 0
+	check_fail $? "Did not match on correct filter"
 
 	tc filter del dev $h2 ingress protocol ip pref 1 handle 101 flower
 	tc filter del dev $h2 ingress protocol ip pref 2 handle 102 flower
···
 	tc_check_packets "dev $h2 ingress" 101 1
 	check_fail $? "Matched on a wrong filter"
 
-	tc_check_packets "dev $h2 ingress" 102 1
-	check_err $? "Did not match on correct filter"
+	tc_check_packets "dev $h2 ingress" 102 0
+	check_fail $? "Did not match on correct filter"
 
 	tc filter del dev $h2 ingress protocol ip pref 1 handle 101 flower
 	tc filter del dev $h2 ingress protocol ip pref 2 handle 102 flower