Random port not reported correctly by webserver module

[wcummings]

1. What version?
   2.1.1

2. What steps will reproduce the problem?

   1. Get a copy of https://github.com/numtel/phantomjs-persistent-server/blob/master/src/phantom-server.js
   2. Change the last line to console.log(server.port, 'Ready.');
   3. Run it passing 0 (random port), and see that server.port returns 0 and not the port its bound to.

3. Which operating system are you using?
   Linux

4. Did you use binary PhantomJS or did you compile it from source?
   Binary

5. Please provide any additional information below.

I wrote a patch I'm currently fashioning into a PR, which will reference this issue as requested in the CONTRIBUTING file.

Assigning a random port comes in handy if you're managing a bunch of phantom instances on one machine. Using 0 is the only race-condition-proof way of assigning a random port, as far as I know.

Here's a case where someone is working around the issue in a pretty heinous way that I didn't want to duplicate in my project:

• https://github.com/baudehlo/node-phantom-simple/blob/master/node-phantom-simple.js#L195-L229
• Allow bridge host and port to be specified via options baudehlo/node-phantom-simple#141