1. Replace raw `docker inspect -f xxx` with `inspectField`, to make code cleaner and more consistent 2. assert the error in function `inspectField*` so we don't need to assert the return value of it every time, this will make inspect easier. Signed-off-by: Zhang Wei <zhangwei555@huawei.com> Upstream-commit: 62a856e9129c9d5cf7db9ea6322c9073d68e3ea4 Component: engine