qemu: command: Use JSON for parameters of -audiodev

'-audiodev' as a modern implementation based on QAPI already takes JSON
as the argument. Convert our code to use it directly.

The declaration of the QAPI types can be found in
'qemu.git/qapi/audio.json'.

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

tests/qemuxml2argvdata/virtio-options-disk-iommu.x86_64-latest.args

@@ -33,7 +33,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/img2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
 -device '{"driver":"virtio-blk-pci","iommu_platform":false,"bus":"pci.0","addr":"0x3","drive":"libvirt-1-format","id":"virtio-disk1"}' \
--audiodev id=audio1,driver=none \
+-audiodev '{"id":"audio1","driver":"none"}' \
 -device '{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.0","addr":"0x4"}' \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
 -msg timestamp=on