qemu-iotests: Fix regression in 136 on aio_read invalid

Commit 093ea232 removed the ability for aio_read and aio_write
to artificially inflate the invalid statistics counters for
block devices, since it no longer flags unaligned offset or
length.  Add 'aio_read -i' and 'aio_write -i' to restore
the ability, and update test 136 to use it.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-id: 1463416983-28318-4-git-send-email-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
