mpd sets a 1s select() timeout for no reason.  This makes mpd wake up
the CPU, consume some cycles just to see there is nothing to do.  We
can save that by specifying NULL instead of a timeout.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7212 09075e82-0dd4-0310-85a5-a0d7c8717e4f