Spring Cloud Netflix Wrong Content-Encoding set when response is coming from RequestContext::getResponseBody and origin response is gzipped

Hi

When modifying the origin response and setting the client response as a String using RequestContext::setResponseBody, the Content-Encoding header gets wrongly set to what was set on the origin response. This caused a non-gzipped stream marked as gzip with the Content-Encoding header being sent back to the client.

I'll submit a PR shortly.

Comment From: spencergibb

Closing in favor of #3680