Since NFS plugin does not support ControllerServiceCapability,
set it to csi.ControllerServiceCapability_RPC_UNKNOWN.
Also set ControllerServer to nil instead of using the default
because ControllerServer is not implemented in NFS plugin.
If this support is added in the future, capabilities need to
be added accordingly.
This patch updates the README for plugins for CSI 0.2.0.
It includes the following changes:
- Updates the CSC tool location
- Removes "get supported versions" because that was removed
from CSI.
