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>
It's used for updating properties of one or more containers, we only
support resource configs for now. It can be extended in the future.
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>