QEMU complains about us not being explicit with setting snapshot so
lets do that. Also as cdroms are RO media we don't need to jump the
hoops of setting up snapshots and replay disks - just declare the
drive is a cdrom and nothing should change.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231211091346.14616-4-alex.bennee@linaro.org>
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