Preserve request headers in our overridden $httpBackend.

lib/ngoverrides.js

@@ -439,16 +439,17 @@ function registerModule(context) {
 
                         var thisRequestId = nextRequestId;
                         nextRequestId++;
+                        // Pass through any headers that were set in the original request
+                        headers = headers || {};
+                        headers.Host = urlParts.host;
                         var req = pendingRequests[thisRequestId] = module.request(
                             {
                                 hostname: urlParts.hostname,
                                 port: urlParts.port,
                                 path: urlParts.pathname +
                                     (urlParts.search ? urlParts.search : ''),
                                 method: reqMethod,
-                                headers: {
-                                    'Host': urlParts.host
-                                }
+                                headers: headers
                             },
                             function (res) {
                                 // ignore responses to aborted requests