stx: docker pod: persist /var/lib/docker

Make sure docker pod's container FS layers are persisted on the host.
Previously, we persisted /var/run/docker in $BUILD_HOME/docker/run, but
that directory contains only sockets and similar files internal to the
docker daemon. This patch changes the helm chart to persist
/var/lib/docker in $BUILD_HOME/docker/var ; that directory contains
docker FS layers & docker images generated during the build.

TESTS
================================
* Start stx-tools containers
* Pull an image inside "stx shell"
* Stop stx-tools containers
* Make $BUILD_HOME/docker/var is not empty
* Re-start stx-tools containers & make sure the previously-pulled image
  still exists and didn't disappear

Story: 2010055
Task: 47861

Change-Id: Ibbd60f48989ecd9663b98da3167e491a9c2493c7
Signed-off-by: Davlet Panech <davlet.panech@windriver.com>

stx/stx-build-tools-chart/stx-builder/dependency_chart/stx-docker/templates/deployment.yaml

@@ -47,8 +47,8 @@ spec:
           volumeMounts:
           - name: shared-workspace
             mountPath: {{ .Values.volumes.sharedWorkspace.mountPath }}
-          - name: docker-run
-            mountPath: {{ .Values.volumes.dockerRun.mountPath }}
+          - name: docker-var
+            mountPath: {{ .Values.volumes.dockerVar.mountPath }}
           resources:
             {{- toYaml .Values.resources | nindent 12 }}
 
@@ -59,9 +59,9 @@ spec:
       - name: shared-workspace
         hostPath:
           path: {{ .Values.global.hostDir }}{{ .Values.volumes.sharedWorkspace.hostPath }}
-      - name: docker-run
+      - name: docker-var
         hostPath:
-          path: {{ .Values.global.hostDir }}{{ .Values.volumes.dockerRun.hostPath }}
+          path: {{ .Values.global.hostDir }}{{ .Values.volumes.dockerVar.hostPath }}
       {{- with .Values.nodeSelector }}
       nodeSelector:
         {{- toYaml . | nindent 8 }}

stx/stx-build-tools-chart/stx-builder/dependency_chart/stx-docker/values.yaml

@@ -15,9 +15,9 @@ volumes:
   sharedWorkspace:
     mountPath: /localdisk
     hostPath: /localdisk
-  dockerRun:
-    mountPath: /var/run/docker
-    hostPath: /docker/run
+  dockerVar:
+    mountPath: /var/lib/docker
+    hostPath: /docker/var
 
 services:
   dockerDaemon: