updating discovery metadata removes "has_auth" from data_mappings and removes "security" from links

[maaikelimper]

Updating the discovery metadata content of a dataset after adding access-control has been added, removes the security-property "has_auth: true" and removes the links with property

"security": {
  "default": {
    "type": "http",
    "scheme": "bearer",
    "description": "Please contact the data provider for access"
  }
}

Related to #775

To reproduce:

• create new dataset
• add access control to dataset using wis2box auth add-token --metadata-id [...]
• update dataset (for example change description)