additionalProperties using ref to file does not generate correctly

Description

Generating a map type in swagger where additionalProperties references a file results in the resulting simplified swagger file being wrong:

Result of the yaml generator

definitions:
  FabricControllerMap:
    type: "object"
    additionalProperties:
      $ref: "./definitions/FabricController.yaml#/FabricController"
  FabricController:
    allOf:
    - $ref: "#/definitions/PlexxiObject"
    - properties:
        apiVersion:
          type: "string"
        connectionFailedCount:
          type: "integer"
          format: "int64"
          readOnly: true
        # Ect.....

Result of the spring code generator

/**
 * FabricControllerMap
 */
@javax.annotation.Generated(value = "io.swagger.codegen.languages.SpringCodegen", date = "2017-01-31T13:48:25.402-05:00")

public class FabricControllerMap extends HashMap<String, DefinitionsFabricControllerYamlFabricController>  {
    // ....

Swagger-codegen version

Latest master

Swagger declaration file content or url

./definitions/FabricController.yaml

FabricController:
  type: object
  description: |
    The abstract representation of all types of Ports.
  allOf:
  - $ref: './definitions/PlexxiObject.yaml#/PlexxiObject'
  - properties:
      apiVersion:
        type: string
      connectionFailedCount:
        type: integer
        format: int64
        readOnly: true
     # ect.....

./definitions/FabricControllerMap.yaml

FabricControllerMap:
  type: object
  additionalProperties:
    $ref: './definitions/FabricController.yaml#/FabricController'

./swagger.yaml

# More above
parameters:
  FabricControllerListBody:
    name: fabricController
    in: body
    required: true
    schema:
      type: array
      items:
        $ref: './definitions/FabricControllerMap.yaml#/FabricControllerMap'

Command line used for generation

lang = "io.swagger.codegen.languages.SwaggerYamlGenerator"

Steps to reproduce

Try to create a map that makes reference to a type declared in a different file.

Related issues

Suggest a Fix

Whatever type resolution for $ref that happens on properties in objects needs to also happen in additionalProperties.

Start with the SwaggerYamlGenerator entry point and reproduce the case using FabricController.yaml, FabricControllerMap.yaml, and swagger.yaml. Compare how the generator resolves the $ref under object properties with the $ref under additionalProperties; done when the simplified Swagger and generated Spring type refer to FabricController correctly.