add pull_config in helm chart

[rayne-Li]

currently, we cannot set pull_config in helm chart if we need to use dragonfly

apiVersion: v1
kind: ConfigMap
metadata:
  name: config
  namespace: model-csi
data:
  config.yaml: |-
    service_name: {{ .Values.config.serviceName }}
    root_dir: {{ .Values.config.rootDir }}
    csi_endpoint: unix:///csi/csi.sock

so, what we want is

apiVersion: v1
kind: ConfigMap
metadata:
  name: config
  namespace: model-csi
data:
  config.yaml: |-
    service_name: {{ .Values.config.serviceName }}
    root_dir: {{ .Values.config.rootDir }}
    csi_endpoint: unix:///csi/csi.sock
    {{- with .Values.config.pullConfig }}
    pull_config:
      {{- toYaml . | nindent 6 }}
    {{- end }}

after that, we can set values in values.yaml

config:
  # ....
  rootDir: xxxxx
      serverscheme: https
  pullConfig:
    dragonfly_endpoint: unix:////var/run/dragonfly/dfdaemon.sock