test: remove non-incremental common.PORT changes

Remove uses of `common.PORT + 1337` where `common.PORT` suffices.

PR-URL: #7055
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Refs: #6990

Author: Trott

test/debugger/helper-debugger-repl.js

@@ -4,7 +4,7 @@ var common = require('../common');
 var assert = require('assert');
 var spawn = require('child_process').spawn;
 
-var port = common.PORT + 1337;
+var port = common.PORT;
 
 var child;
 var buffer = '';

test/debugger/test-debugger-client.js

@@ -4,7 +4,7 @@ var common = require('../common');
 var assert = require('assert');
 var debug = require('_debugger');
 
-var debugPort = common.PORT + 1337;
+var debugPort = common.PORT;
 debug.port = debugPort;
 var spawn = require('child_process').spawn;