block: qemu-iotests - fix test 070 (vhdx)

VHDX test 070 failed, due to different output from qemu-io / qemu
when opening an image read-only that contains a log file.  Filter
the output, and update the expected results to match the correct
output.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>