refactor: Deduplicate env var

[koooge]

Hi there, telegraf-ds's daemonset has the duplicated env var HOSTIP.

...
      containers:
      - env:
        - name: HOSTIP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.hostIP
        - name: HOSTNAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: spec.nodeName
        - name: HOSTIP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.hostIP
...

[Bozz95]

I think this is the right choice to remove this env var "HOSTIP" from the values.
Leaving the HOSTIP declaration only in the template file will enure that this helm installation will work regardless of the resolvable host ip within the containers.