Fix the flushing of messages when switching to Websocket

We now flush messages that are specific to cowboy_http only.

Stream handlers should also flush their own specific messages
if necessary, although timeouts will be flushed regardless
of where they originate from.

Also renames the http_SUITE to old_http_SUITE to distinguish
new tests from old tests. Most old tests need to be removed
or converted eventually as they're legacy tests from Cowboy 1.0.

test/old_http_SUITE_data/rest_patch_resource.erl

@@ -0,0 +1,38 @@
+-module(rest_patch_resource).
+
+-export([init/2]).
+-export([allowed_methods/2]).
+-export([content_types_provided/2]).
+-export([get_text_plain/2]).
+-export([content_types_accepted/2]).
+-export([patch_text_plain/2]).
+
+init(Req, Opts) ->
+	{cowboy_rest, Req, Opts}.
+
+allowed_methods(Req, State) ->
+	{[<<"HEAD">>, <<"GET">>, <<"PATCH">>], Req, State}.
+
+content_types_provided(Req, State) ->
+	{[{{<<"text">>, <<"plain">>, []}, get_text_plain}], Req, State}.
+
+get_text_plain(Req, State) ->
+	{<<"This is REST!">>, Req, State}.
+
+content_types_accepted(Req, State) ->
+	case cowboy_req:method(Req) of
+		<<"PATCH">> ->
+			{[{{<<"text">>, <<"plain">>, []}, patch_text_plain}], Req, State};
+		_ ->
+			{[], Req, State}
+	end.
+
+patch_text_plain(Req, State) ->
+	case cowboy_req:read_body(Req) of
+		{ok, <<"stop">>, Req0} ->
+			{stop, cowboy_req:reply(400, Req0), State};
+		{ok, <<"false">>, Req0} ->
+			{false, Req0, State};
+		{ok, _Body, Req0} ->
+			{true, Req0, State}
+	end.