Add TODO for BusyBox support

include/tests_firewalls

@@ -108,6 +108,7 @@
     # Test        : FIRE-4508
     # Description : Check iptables chain policies
     # Notes       : Suggestions are currently disabled, until related page and documentation is available
+    # TODO        : grep -z is not supported on BusyBox
     if [ ! "${IPTABLESBINARY}" = "" -a ${IPTABLES_ACTIVE} -eq 1 ]; then PREQS_MET="YES"; else PREQS_MET="NO"; fi
     Register --test-no FIRE-4508 --preqs-met ${PREQS_MET} --os Linux --weight L --network NO --root-only YES --category security --description "Check used policies of iptables chains"
     if [ ${SKIPTEST} -eq 0 ]; then