iotests: Check for the availability of the required devices in 267 and 127

iotests: Check for the availability of the required devices in 267 and 127

We are going to enable 127 in the "auto" group, but it only works if
virtio-scsi and scsi-hd are available - which is not the case with
QEMU binaries like qemu-system-tricore for example, so we need a
proper check for the availability of these devices here.

A very similar problem exists in iotest 267 - it has been added to
the "auto" group already, but requires virtio-blk and thus currently
fails with qemu-system-tricore for example. Let's also add aproper
check there.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 20200121095205.26323-5-thuth@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>