Wrong schema definition for jsonschema validation

[Masaki UENO]

In the Tacker Antelope implementation, schema definition of `CpProtocolData` has a wrong enum definition, which causes validation error when a LCM request is sent from clients.

When an InstantiateVnfRequest is sent from a client to Tacker, the client received 400 Bad Request.

```
{"status": 400, "detail": "Invalid input for field/attribute layerProtocol. Value: IP_OVER_ETHERNET. 'IP_OVER_ETHERNET' is not one of 'IP_OVER_ETHERNET'", "title": "Bad Request"}
```

Parameter of InstantiateVnfRequest is as follows:

```
{
  "flavourId": "simple",
  "instantiationLevelId": "instantiation_level_1",
  "extVirtualLinks": [
    {
      "id": "270f1e37-0d38-4e75-869a-158737d48a1a",
      "resourceId": "270f1e37-0d38-4e75-869a-158737d48a1a",
      "extCps": [
        {
          "cpdId": "VDU1_CP1",
          "cpConfig": {
            "VDU1_CP1": {
              "cpProtocolData": [
                {
                  "layerProtocol": "IP_OVER_ETHERNET",
                  "ipOverEthernet": {
                    "ipAddresses": [
                      {
                        "type": "IPV4",
                        "numDynamicAddresses": 1
                      }
                    ]
                  }
                }
              ]
            }
          }
        },
        {
          "cpdId": "VDU2_CP1",
          "cpConfig": {
            "VDU2_CP1": {
              "cpProtocolData": [
                {
                  "layerProtocol": "IP_OVER_ETHERNET",
                  "ipOverEthernet": {
                    "ipAddresses": [
                      {
                        "type": "IPV4",
                        "fixedAddresses": [
                          "192.168.200.101"
                        ]
                      }
                    ]
                  }
                }
              ]
            }
          }
        }
      ]
    }
  ]
}
```

In the sample described in JSON schema document[1], value type of "enum" is array. However, JSON schema of CpProtocolData is defined as follows[2]:

```
CpProtocolData = {
    'type': 'object',
    'properties': {
        'layerProtocol': {
            'type': 'string',
            'enum': 'IP_OVER_ETHERNET'},
        'ipOverEthernet': IpOverEthernetAddressData,
    },
    'required': ['layerProtocol'],
    'additionalProperties': True,
}
```

I think the root cause of this behavior is that `properties.layerProtocol.enum` is not defined as array, thus the following will resolve this issue.

```
CpProtocolData = {
    'type': 'object',
    'properties': {
        'layerProtocol': {
            'type': 'string',
            'enum': ['IP_OVER_ETHERNET']},
        'ipOverEthernet': IpOverEthernetAddressData,
    },
    'required': ['layerProtocol'],
    'additionalProperties': True,
}
```

--- References ---

[1] https://json-schema.org/understanding-json-schema/reference/enum
[2] https://opendev.org/openstack/tacker/src/branch/stable/2023.1/tacker/sol_refactored/api/schemas/common_types.py#L194-L199