This fix made several updates: 1. Update opts.MemBytes so that default value will not show up. The reason is that in case a default value is decided by daemon, instead of client, we actually want to not show default value. 2. Move `docker run/create/build` to use opts.MemBytes for `--shm-size` This is to bring consistency between daemon and docker run 3. docs updates. Signed-off-by: Yong Tang <yong.tang.github@outlook.com>