Implement config for airgap_parameters

[snowch]

PUT /api/v2/config/k8s HTTP/1.1
Host: 127.0.0.1:8080
Content-Length: 280
Accept-Encoding: gzip, deflate
REMOTE_ADDR: 185.69.144.159
Accept: */*
User-Agent: python-requests/2.6.0 CPython/2.7.5 Linux/3.10.0-1127.18.2.el7.x86_64
Connection: keep-alive
X-BDS-SESSION: /api/v2/session/bdbc5cda-991f-4196-a63a-65612f625113
Authorization: /api/v2/session/bdbc5cda-991f-4196-a63a-65612f625113

{
  "airgap_parameters": {
    "repo_gpg_key": "https://myurl.com",
    "container_repo_username": "adm",
    "rpm_gpg_key": "https://myurl.com",
    "baseurl": "https://myurl.com",
    "is_secure_container_repo": true,
    "container_repo_password": "pass123",
    "container_repo_url": "www.example.com:1234"
  }
}
HTTP/1.1 204 No Content
Access-Control-Allow-Origin: *
Content-Length: 0
Content-Type: text/plain
Date: Fri, 31 Jul 2020 22:29:14 GMT
Server: HPE Ezmeral Container Platform 5.1

[snowch]

GET /api/v2/config/k8s HTTP/1.1
Host: 127.0.0.1:8080
Accept-Encoding: gzip, deflate
REMOTE_ADDR: 185.69.144.159
Accept: */*
User-Agent: python-requests/2.6.0 CPython/2.7.5 Linux/3.10.0-1127.18.2.el7.x86_64
Connection: keep-alive
X-BDS-SESSION: /api/v2/session/bdbc5cda-991f-4196-a63a-65612f625113
Authorization: /api/v2/session/bdbc5cda-991f-4196-a63a-65612f625113

HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Content-Length: 340
Content-Type: application/json
Date: Fri, 31 Jul 2020 22:29:20 GMT
Server: HPE Ezmeral Container Platform 5.1

{
  "_links": {
    "self": {
      "href": "api/v2/config/k8s"
    }
  },
  "airgap_parameters": {
    "is_secure_container_repo": true,
    "container_repo_url": "www.example.com:1234",
    "container_repo_username": "adm",
    "container_repo_client_certificate": "",
    "baseurl": "https://myurl.com",
    "rpm_gpg_key": "https://myurl.com",
    "repo_gpg_key": "https://myurl.com",
    "support_rpm_repo": true
  }
}