The 'raw' driver without any special configuration is not needed and
creates overhead in qemu.
Stop using the 'raw' format driver in cases when it's not needed. A
special case when it is needed is for FD passed images with only a
single writable FD passed, where we need an overlay driver to properly
reflect the 'read-only' flag.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>