Hardcoded image for curl in solr initContainer

Hi, I am setting up XWiki in an Openshift environment with internet restrictions, pulling images through our internal registry.

In templates/solr-statefulset.yaml, the download-cores init container uses a hardcoded image:

    spec:
      {{- if .Values.solr.downloadCores.enabled }}
      initContainers:
        - name: download-cores
          image: curlimages/curl
          env:
          {{- range .Values.solr.extraEnvVars }}
            - name: {{ .name  }}
              value: {{ .value | quote }}
          {{- end }}
          command: ['/bin/sh', '-c']

This hard coding of curlimages/curl will directly reference to docker.io.

Perhaps this would be a better solution in templates/solr-statefulset.yaml

        - name: download-cores
          image: {{ .Values.solr.downloadCores.image | quote }}

defaulting with:

solr:
  downloadCores:
    enabled: true
    image: "curlimages/curl:latest" 

It would also be an improvement for on premise installations with internet restrictions to allow the 2 variables: SOLR_CORE_URL and SOLR_MINIMAL_CORE_URL be configurable via values

Thanks!