qemu-iotests: Filter qemu-io output in 025

Signed-off-by: Fam Zheng <famz@redhat.com>
qemu-iotests: Filter out 'qemu-io> ' prompt

This removes "qemu-io> " prompt from qemu-io output in _filter_qemu_io,
and updates all the output files.

Signed-off-by: Fam Zheng <famz@redhat.com>