Support configurable docker root directory

[KimMJ]

I tried to use ze-kubernetes-collector and found a issue.

We are using /path/to/docker as a docker-root-directory.
It is not mounted as default and cannot be added through custom values file.
So log-collector cannot access to our container's stdout/err logs.

So I added volumeMounts and volumes in Daemonset spec.
I think it is not just our special case.
It will be nice to be able to configure root directory in values file