unifiedId UserId submodule should always make a secure call

modules/unifiedIdSystem.js

@@ -39,7 +39,7 @@ export const unifiedIdSubmodule = {
       return;
     }
     // use protocol relative urls for http or https
-    const url = configParams.url || `//match.adsrvr.org/track/rid?ttd_pid=${configParams.partner}&fmt=json`;
+    const url = configParams.url || `https://match.adsrvr.org/track/rid?ttd_pid=${configParams.partner}&fmt=json`;
 
     const resp = function (callback) {
       ajax(url, response => {

test/spec/modules/userId_spec.js

@@ -1076,7 +1076,7 @@ describe('User ID', function() {
 
       expect(server.requests).to.be.empty;
       events.emit(CONSTANTS.EVENTS.AUCTION_END, {});
-      expect(server.requests[0].url).to.equal('//match.adsrvr.org/track/rid?ttd_pid=rubicon&fmt=json');
+      expect(server.requests[0].url).to.equal('https://match.adsrvr.org/track/rid?ttd_pid=rubicon&fmt=json');
     });
 
     it('callback for submodules that always need to refresh stored id', function(done) {