Remove redfish message from http client

HttpClient these days is intended to be a generic feature.  It should
not be relying directly on Redfish messages.  In this case, we only ever
rely on the return code internally, so replace messages with a simple
bad_gateway.

Tested: Code compiles.  Unit tests pass.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ie4bd65dc0b90b75f61ab0e31ca535eefbf0f4ebb
diff --git a/http/http_client.hpp b/http/http_client.hpp
index 1568b25..63c2611 100644
--- a/http/http_client.hpp
+++ b/http/http_client.hpp
@@ -299,7 +299,7 @@
             // We want to return a 502 to indicate there was an error with the
             // external server
             res.clear();
-            redfish::messages::operationFailed(res);
+            res.result(boost::beast::http::status::bad_gateway);
 
             if (retryPolicy.retryPolicyAction == "TerminateAfterRetries")
             {