Fix regcache for registry 3.x config loading (#1285)

registry:3 ignores REGISTRY_CONFIGURATION_PATH and serves the built-in
/etc/distribution/config.yml, so the pull-through proxy config was never
loaded (every pull returned manifest unknown). Pass the config path as an
arg instead, and add the age/interval/dryrun/dontcleanuptmpdir fields that
3.x requires when uploadpurging is enabled.

Signed-off-by: Arnob Kumar Saha <arnob@appscode.com>
Signed-off-by: Tamal Saha <tamal@appscode.com>
Co-authored-by: Tamal Saha <tamal@appscode.com>

Author: ArnobKumarSaha

charts/regcache/templates/configmap.yaml

@@ -21,6 +21,10 @@ data:
       maintenance:
         uploadpurging:
           enabled: true
+          age: 72h
+          interval: 24h
+          dryrun: false
+          dontcleanuptmpdir: false
     http:
       addr: :5000
       headers:

charts/regcache/templates/deployment.yaml

@@ -40,14 +40,13 @@ spec:
         {{- end }}
         image: "{{ include "regcache.image.registry" . }}/{{ .Values.image.repository }}:{{ .Values.image.tag }}"
         imagePullPolicy: {{ .Values.image.pullPolicy }}
+        args: ["serve", "/etc/docker/registry/config.yml"]
         ports:
         - name: registry
           containerPort: 5000
           protocol: TCP
-        env:
-        - name: REGISTRY_CONFIGURATION_PATH
-          value: /etc/docker/registry/config.yml
         {{- if .Values.username }}
+        env:
         - name: REGISTRY_PROXY_USERNAME
           valueFrom:
             secretKeyRef: