Fix test-network.sh argument parsing

The bash on one of my machines didn't understand the question mark
correctly, it didn't end up accepting flavor. We can spell it out
explicitly.

src/test/test-network.sh

@@ -13,7 +13,7 @@ do
       export TOR_DIR="$2"
       shift
     ;;
-    --flavo?r|--network-flavo?r)
+    --flavor|--flavour|--network-flavor|--network-flavour)
       export NETWORK_FLAVOUR="$2"
       shift
     ;;