Only overwrite referrer if this is an unload call

We check the referrer many times for browsers that don't support
navtiming.  For this to work, we need the referrer to be correct until
after we've read the start time correctly.  To make sure this works, we
set the referrer only in the unload handler.

plugins/rt.js

@@ -45,7 +45,9 @@ impl = {
 		subcookies = BOOMR.utils.getSubCookies(BOOMR.utils.getCookie(this.cookie)) || {};
 		// We use document.URL instead of location.href because of a bug in safari 4
 		// where location.href is URL decoded
-		subcookies.r = d.URL.replace(/#.*/, '');
+		if(how === "ul") {
+			subcookies.r = d.URL.replace(/#.*/, '');
+		}
 
 		if(how === "cl") {
 			if(url) {