iotests: Add test of recent fix to 'qemu-img measure'

The new test 190 ensures we don't regress back to an infinite loop when
measuring the size of a 2T+ qcow2 image.  I did not append to test 178,
because that test is also designed to run with format 'raw'; also, this
gives us some coverage of the measure command under the quick group.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
