Use the none audio device to eliminate ALSA errors

BUG: 128941875
Test: TreeHugger
Change-Id: Ie51ad3f2191cc384b8051d1903e95187e88525ef
diff --git a/host/libs/vm_manager/cf_qemu.sh b/host/libs/vm_manager/cf_qemu.sh
index 244fae2..ac63bbe 100755
--- a/host/libs/vm_manager/cf_qemu.sh
+++ b/host/libs/vm_manager/cf_qemu.sh
@@ -217,4 +217,5 @@
   args+=(-device "vhost-vsock-pci,guest-cid=${vsock_guest_cid}")
 fi
 
+export QEMU_AUDIO_DRV=none
 exec_run "${qemu_binary}" "${args[@]}"