Reverted to the version of audio_pipe.c prior to the last major change and used a different method to open the pipe for writing.

I am using shairport with forked-daapd. The prior changes submitted by ejurgensen were not reliable for me. After starting a couple AirPlay streams, shairport would become unresponsive, and I would have to restart it. I reverted to the prior version of audio_pipe.c and made changes. To achieve the functionality that ejurgensen added, I first open the pipe for reading, opening it for writing, and then close the read fd. I have been using this for a couple weeks with no issues.

This is my first attempt at using git and GitHub, so I apologize if I haven't made this request properly.