[Kotlin] Duplicated properties in constructor of data class

Description

Codegen generates duplicated properties in constructor.

Swagger-codegen version

2.4.2

Swagger declaration file content or url

"swagger": "2.0"

AcceptTeamInvitationRequest:
    allOf:
      - $ref: '#/definitions/UserId'
      - properties:
          invitationCode:
            type: string
    type: object
    required:
      - invitationCode

UserId:
    type: object
    properties:
      userId:
        type: string

Generates this corrupt kotlin file

import io.swagger.client.models.UserId

/**
 * 
 * @param userId 
 * @param invitationCode 
 */
data class AcceptTeamInvitationRequest (
    val userId: kotlin.String? = null,
    val invitationCode: kotlin.String? = null,
    val userId: kotlin.String? = null,
    val invitationCode: kotlin.String? = null
) {

} 

Command line used for Kotlin generation

swagger-codegen generate -l kotlin -i swagger.api.yaml -c swagger-codegen.config.json -o my_directory

Reproduce the issue with swagger.api.yaml and swagger-codegen.config.json using the shown Kotlin generation command. Trace the Kotlin code-generation entry point and templates responsible for composing inherited and local properties. Done means AcceptTeamInvitationRequest is generated with userId and invitationCode only once, while preserving the expected data-class constructor.