Handle new open-source standard for config.json

[outscale-frl]

Now we just handle the new folder with .osc/config.json but we need to be compatible with the new config.jsonstandard:

{
  "default": {
    "access_key": "F4K4T706S9XKGEXAMPLE",
    "secret_key": "E4XJE8EJ98ZEJ18E4J9ZE84J19Q8E1J9S87ZEXAMPLE",
    "x509_client_cert": "/etc/secret/client.crt",
    "x509_client_key": "/etc/secret/client.key",
    "protocol": "https",
    "method": "post",
    "region": "eu-west-2",
    "endpoints": {
      "api": "api.eu-west-2.outscale.com/api/v1",
      "oos": "oos.eu-west-2.outscale.com"
    }
  }
}