Cherry-pick #16205 to 7.x: Fix: don't miss address scheme

[mtojek]

Cherry-pick of PR #16205 to 7.x branch. Original message:

While working on the Ceph module (#7723) I've prepared the following setup for a new metric set:

modules.d/ceph.yml:

- module: ceph
  metricsets:
    - mgr_cluster_health
  hosts: [ "https://ceph-restful:8003" ]
  username: "demo"
  password: "51dd94b3-f865-4f63-af79-9efb9130cd7f"
  ssl.verification_mode: "none"

module/ceph/mgr_cluster_health:

default: true
input:
  module: http
  metricset: json
  defaults:
    method: POST
    namespace: "json_namespace"
    basepath: "/request"
    headers:
      Content-Type: application/json
    query:
      wait: "1"
    body: '{"prefix": "status", "format": "json"}'

processors:
  - extract_array:
      field: http.json_namespace.finished
      mappings:
        ceph.request: 0
  - decode_json_fields:
      fields: ["ceph.request.outb"]
      process_array: true
      target: "ceph.mgr_cluster_status.output"
  - drop_fields:
      fields: ["http", "ceph.request"]

The problem: Ceph's request API is accessible via HTTPS (by default) and the information about protocol scheme (https://) is getting lost in runtime.