Allow (websocket) upgrade even without persistent connection for normal http request.

(note: this allows to use websocket in single-threaded mode, and avoid the keep-alive-timeout delay before websocket begins its execution)

library/server/ewsgi/connectors/standalone/src/wgi_standalone_response_stream.e

@@ -110,8 +110,10 @@ feature -- Header output operation
 					if
 						not l_connection.is_case_insensitive_equal_general ("close")
 					then
+						if not l_connection.is_case_insensitive_equal_general ("upgrade") then
 							s.replace_substring ("Connection: close", i + 1, j - 1)
 						end
+					end
 				elseif not is_http_version_1_0 then
 						-- HTTP/1.1: always return "close" since persistent connection is not supported.
 					s.append ("Connection: close")