Description:
By default, RESTEasy returns wrong Content-Encoding data if client request gzip data and if RESTEasy end-point contains @GZiP annotation

1. Server contains end-point with @GZIP annotation, for example this:

       @GET
       @Path("/echo")
       @GZIP
       String echo(@QueryParam("name") String message);

2. RESTEasy client send request with "Accept-Encoding: gzip, deflate"
3. By default, server doesn't use GZIPDecodingInterceptor, GZIPEncodingInterceptor and AcceptEncodingGZIPFilter. So server doesn't compress data
4. server sends "Content-Encoding: gzip" in header of response, although data is not compressed

Steps to reproduce in EAP 7.1:

1. download attached reproducer
2. mvn clean package -Djboss.home=${JBOSS_HOME} -Dmaven.test.failure.ignore=true

Some technical details from same issue in master branch:
Server returns gzip in header , because "gzip" is in "Set<String> encodings;" [4] from ServerContentEncodingAnnotationFilter class. Resteasy checks all annotations in end-point method:

@GET
@Path("/echo")
@GZIP
String echo(@QueryParam("name") String message);

Resteasy find @GZIP annotation and check, if @GZIP annotation has @ContentEncoding annotation here [5]. GZIP annotation has @ContentEncoding, see [6]. So Resteasy return gzip in response header, although Resteasy doesn't compress data.

[4] https://github.com/resteasy/Resteasy/blob/master/resteasy-jaxrs/src/main/java/org/jboss/resteasy/plugins/interceptors/ServerContentEncodingAnnotationFilter.java#L31
[5] https://github.com/resteasy/Resteasy/blob/master/resteasy-jaxrs/src/main/java/org/jboss/resteasy/plugins/interceptors/ServerContentEncodingAnnotationFeature.java#L49
[6] https://github.com/resteasy/Resteasy/blob/master/resteasy-jaxrs/src/main/java/org/jboss/resteasy/annotations/GZIP.java#L14