Fix missing volume after refactor

Signed-off-by: Steven Sheehy <ssheehy@firescope.com>

production/helm/loki-stack/Chart.yaml

 name: loki-stack
-version: 0.6.0
+version: 0.6.1
 appVersion: 0.0.1
 kubeVersion: "^1.10.0-0"
 description: "Loki: like Prometheus, but for logs."

production/helm/promtail/Chart.yaml

 name: promtail
-version: 0.6.0
+version: 0.6.1
 appVersion: 0.0.1
 kubeVersion: "^1.10.0-0"
 description: "Responsible for gathering logs and sending them to Loki"

production/helm/promtail/values.yaml

@@ -82,11 +82,17 @@ tolerations:
 
 # Extra volumes to scrape logs from
 volumes:
+- name: docker
+  hostPath:
+    path: /var/lib/docker/containers
 - name: pods
   hostPath:
     path: /var/log/pods
 
 volumeMounts:
+- name: docker
+  mountPath: /var/lib/docker/containers
+  readOnly: true
 - name: pods
   mountPath: /var/log/pods
   readOnly: true