skypiax: let's drain the audiopipe to empty, each time we read from it. This avoid accumulation of unread samples in the pipe buffer (was cause of delays?). Anyway, now latency is lower. Let's check if it breaks on windoz

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@14369 d0543943-73ff-0310-b7d9-9358b9ac24b2