add some common examples for docker images, and tell the user what -a filters out Upstream-commit: 82cdd21a3492789a47fc4c3bb3f8a4d85b89d14c Component: engine
add some common examples for docker images, and tell the user what -a filters out Upstream-commit: 82cdd21a3492789a47fc4c3bb3f8a4d85b89d14c Component: engine