Update renderAd to replace ${AUCTION_PRICE} in adUrl (#1795)

* Modify `adUrl` instead of `url` with bid price

The `bid.url` parameter is not used to render the iframe for an ad that
returns a url but is being treated as such when the auction price is
being inserted. This commit inserts the auction price into `bid.adUrl`
which is used to render the ad.

* Use the key for adUrl instead of using url

Instead of renaming the parameter `adUrl` to `url` for the rendering
function, use `adUrl` to be consistent with the key value returned in
the bid object.

src/prebid.js

@@ -282,14 +282,14 @@ $$PREBID_GLOBAL$$.renderAd = function (doc, id) {
       if (bid) {
         // replace macros according to openRTB with price paid = bid.cpm
         bid.ad = utils.replaceAuctionPrice(bid.ad, bid.cpm);
-        bid.url = utils.replaceAuctionPrice(bid.url, bid.cpm);
+        bid.adUrl = utils.replaceAuctionPrice(bid.adUrl, bid.cpm);
         // save winning bids
         $$PREBID_GLOBAL$$._winningBids.push(bid);
 
         // emit 'bid won' event here
         events.emit(BID_WON, bid);
 
-        const { height, width, ad, mediaType, adUrl: url, renderer } = bid;
+        const { height, width, ad, mediaType, adUrl, renderer } = bid;
 
         if (renderer && renderer.url) {
           renderer.render(bid);
@@ -299,13 +299,13 @@ $$PREBID_GLOBAL$$.renderAd = function (doc, id) {
           doc.write(ad);
           doc.close();
           setRenderSize(doc, width, height);
-        } else if (url) {
+        } else if (adUrl) {
           const iframe = utils.createInvisibleIframe();
           iframe.height = height;
           iframe.width = width;
           iframe.style.display = 'inline';
           iframe.style.overflow = 'hidden';
-          iframe.src = url;
+          iframe.src = adUrl;
 
           utils.insertElement(iframe, doc, 'body');
           setRenderSize(doc, width, height);