tests/qtest: Move mkimg() and have_qemu_img() from libqos to libqtest

These two functions can be useful for other qtests beside the
qos-test, too, so move them to libqtest instead.

Message-Id: <20230704071655.75381-3-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
4 files changed