[general] date examples are converted and output as date-time in generated json

Description

Using yaml input, we among other things also generate json.
Adding an example to a date results in the date being parsed and serialized back to string as date-time

Swagger-codegen version

2.2.3, generator cxf-jaxrs-client

Swagger declaration file content or url

yaml input

swagger: '2.0'
info:
  title: Member
  version: '2.0'
basePath: /education-group/v2
paths:
  /:
    get:
      responses:
        '200':
          description: members
          schema:
            $ref: '#/definitions/Member'
definitions:
  Member:
    type: object
    properties:
      endDate:
        type: string
        format: date
        example: 2117-01-01

json output

        "endDate" : {
          "type" : "string",
          "format" : "date",
          "example" : "2117-01-01T00:00:00.000+0000",
        }

Command line used for generation

swagger-codegen-cli doesn't support json, but html works as well so this seems to be a general problem rather than java or html

java -jar swagger-codegen-cli.jar generate -i input.yaml -l html

Steps to reproduce

1. save input.yaml from the issue
2. java -jar swagger-codegen-cli.jar generate -i input.yaml -l html
3. grep '"endDate"' index.html
   "endDate" : "2117-01-01T00:00:00.000+0000"

Related issues/PRs

N/A

Suggest a fix/enhancement

Either parse and return date as date instead of date-time, or simply treat the example an opaque string.

Reproduce the issue with input.yaml using swagger-codegen-cli.jar and the cxf-jaxrs-client generator, then inspect the generated index.html output for the endDate example. The fix is complete when the date example remains "2117-01-01" or is represented as a date rather than being converted to date-time.