Turn ignoreRequestBody into no-const method

As nghttp2 req is passed, it is probable that user implementation,
analyzes data and indexes processing on server cache for
further stage (receive()). Thus, once ignored (or not) the
request body received, the thing is that receive() could be
not repeating again same processing of received data.

include/ert/http2comm/Http2Server.hpp

@@ -203,7 +203,7 @@ class Http2Server
     *
     * @return Return the boolean about ignoring request body copy. Default implementation returns 'false'.
     */
-    virtual bool ignoreRequestBody(const nghttp2::asio_http2::server::request& req) const {
+    virtual bool ignoreRequestBody(const nghttp2::asio_http2::server::request& req) {
         return false;
     }