tests/30-audio: Fix dd command, better pulseaudio test.
tests/30-audio: Fix dd command, better pulseaudio test.

Incorrect dd direction might be causing the test to fail
occasionally (#1101).

dragon788/chroagh,armgong/chroagh,JDGBOLT/chroagh,dragon788/chroagh,JDGBOLT/chroagh,rperce/chroagh,armgong/chroagh,elkangaroo/chroagh,rperce/chroagh,dragon788/chroagh,dragon788/chroagh,rperce/chroagh,JDGBOLT/chroagh,rperce/chroagh,JDGBOLT/chroagh,elkangaroo/chroagh,armgong/chroagh,dragon788/chroagh,dragon788/chroagh,rperce/chroagh,armgong/chroagh,elkangaroo/chroagh,elkangaroo/chroagh,elkangaroo/chroagh,armgong/chroagh,JDGBOLT/chroagh,rperce/chroagh,armgong/chroagh,JDGBOLT/chroagh,elkangaroo/chroagh