don't lie about reachable address

when app.http.address is specified. Instead just tell the user that
scope is reachable where they said.

Also, complain when the address is specified on D4M since there are
a bunch of hard-coded port 4040 in place for that.

Fixes #1190.

scope

@@ -115,6 +115,10 @@ check_probe_only() {
     echo "${ARGS}" | grep -q -E "\-\-no\-app|\-\-service\-token|\-\-probe\-only"
 }
 
+check_listen_address_arg() {
+    echo "${ARGS}" | grep -q -E "\-\-app\.http\.address"
+}
+
 check_docker_for_mac() {
     [ "$(uname)" = "Darwin" ] \
         && [ -S /var/run/docker.sock ] \
@@ -251,6 +255,10 @@ case "$COMMAND" in
             # - https://github.com/weaveworks/scope/issues/1411
             # - https://forums.docker.com/t/ports-in-host-network-namespace-are-not-accessible/10789
             dry_run "$@"
+            if check_listen_address_arg; then
+                echo "--app.http.address argument not supported on Docker for Mac" >&2
+                exit 1
+            fi
             check_not_running "$SCOPE_APP_CONTAINER_NAME" "$SCOPE_IMAGE_NAME"
             check_not_running "$SCOPE_CONTAINER_NAME" "$SCOPE_IMAGE_NAME"
             docker rm -f "$SCOPE_APP_CONTAINER_NAME" >/dev/null 2>&1 || true
@@ -266,12 +274,15 @@ case "$COMMAND" in
         dry_run "$@"
         launch "$@"
         if ! check_probe_only; then
-            # shellcheck disable=SC2086
-            IP_ADDRS=$(docker run --rm $USERNS_HOST --net=host --entrypoint /bin/sh "$SCOPE_IMAGE" -c "$IP_ADDR_CMD")
-            # shellcheck disable=SC2086
-            print_app_endpoints $IP_ADDRS
+            if check_listen_address_arg; then
+                echo "Weave Scope is reachable at the address specified with --app.http.address" >&2
+            else
+                # shellcheck disable=SC2086
+                IP_ADDRS=$(docker run --rm $USERNS_HOST --net=host --entrypoint /bin/sh "$SCOPE_IMAGE" -c "$IP_ADDR_CMD")
+                # shellcheck disable=SC2086
+                print_app_endpoints $IP_ADDRS
+            fi
         fi
-
         ;;
 
     stop)