Remove mapping to /host/lib from fluentd-gcp container.

This mapping is no longer needed since fluentd-gcp v2.0.16, in which it
started using a container image based on Debian Stretch, in which the
systemd libraries already include support for all the supported
compression algorithms.

The /run.sh in the image no longer accesses /host/lib anyways, so let's
stop mapping it here.

Related changes:
- fluentd-gcp on GoogleCloudPlatform/k8s-stackdriver#101
- fluentd-es on GoogleCloudPlatform/google-fluentd#80

cluster/addons/fluentd-elasticsearch/fluentd-es-ds.yaml

@@ -92,9 +92,6 @@ spec:
         - name: varlibdockercontainers
           mountPath: /var/lib/docker/containers
           readOnly: true
-        - name: libsystemddir
-          mountPath: /host/lib
-          readOnly: true
         - name: config-volume
           mountPath: /etc/fluent/config.d
       nodeSelector:
@@ -107,10 +104,6 @@ spec:
       - name: varlibdockercontainers
         hostPath:
           path: /var/lib/docker/containers
-      # It is needed to copy systemd library to decompress journals
-      - name: libsystemddir
-        hostPath:
-          path: /usr/lib64
       - name: config-volume
         configMap:
           name: fluentd-es-config-v0.1.4