iojs debug -p <pid> starts debugger in debug client #889

$ out/Release/iojs --debug-brk benchmark/http_simple.js 
Debugger listening on port 5858

# from another terminal window
$ out/Release/iojs debug -p $(pgrep iojs)
< Error: listen EADDRINUSE :::5858
<     at Object.exports._errnoException (util.js:734:11)
<     at exports._exceptionWithHostPort (util.js:757:20)
<     at Agent.Server._listen2 (net.js:1155:14)
<     at listen (net.js:1181:10)
<     at Agent.Server.listen (net.js:1268:5)
<     at Object.start (_debug_agent.js:21:9)
<     at startup (node.js:68:9)
<     at node.js:799:3
connecting to port 5858... ok
break in benchmark/http_simple.js:1
> 1 var path = require('path'),
  2     exec = require('child_process').exec,
  3     http = require('http');
debug>