Fix a bug in Java RestTemplate ApiClient.mustache that ApiKey in cookie is not handled.

Code to handle cookieParams when location is "cookie" already exists, which was merged in #4155:

To test, you can create a security schema such as:

securitySchemes:
  ExampleCookieAuth:
    type: apiKey
    in: cookie
    name: session

This should send a Cookie header to server like Cookie: session=12345

@wing328

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