net.http.server: Strip port from Host header in IPv6 friendly way (fix #1302)

E.g. given `[::1]:5280` it would previously result in only `[` instead
of the correct `[::1]`

net/http/server.lua

@@ -207,7 +207,7 @@ function handle_request(conn, request, finish_cb)
 	};
 	conn._http_open_response = response;
 
-	local host = (request.headers.host or ""):match("[^:]+");
+	local host = (request.headers.host or ""):gsub(":%d+$","");
 
 	-- Some sanity checking
 	local err_code, err;