When `docker inspect` is invoked, it is possible to pass a flag of
`-s` for container types to display size information. If `-s` is used
for non-container types then a warning `WARNING: --size ignored for volume`
will show up.
However, currently `WARNING: --size ignored for volume` will show up even
when `-s` is not passed to `docker inspect` for non-container types.
This fix fixes this issue by checking if `-s` has been passed or not (`getSize`).
Also, since image inspect does not support `-s`, `IsSizeSupported` has been changed
to false for images.
This fix is tested manually.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
