removed unwanted extra arguments from the helm templates
and added a single value kubeletDir to make the kubelet
root-dir configurable.
previously used variables like socketDir,registrationDir
and pluginDir is removed now because if we have the kubelet
path we can derive all other required path for cephcsi to
work properly.
fixes: #1475
Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>