qemu: command: Always assume QEMU_CAPS_AUDIODEV

Generate only new version of the '-audiodev' commandline. The leftover
old code and validation will be removed in subsequent patches.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

tests/qemuxml2argvdata/clock-variable.args

@@ -6,7 +6,6 @@ LOGNAME=test \
 XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
 XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
 XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
-QEMU_AUDIO_DRV=none \
 /usr/bin/qemu-system-i386 \
 -name guest=QEMUGuest1,debug-threads=on \
 -S \
@@ -29,5 +28,6 @@ QEMU_AUDIO_DRV=none \
 -usb \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 \
+-audiodev '{"id":"audio1","driver":"none"}' \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \
 -msg timestamp=on