restiming entries not added to beacon on xhr_load

[vkbandi]

Hi,

When xhr_load event is invoked, the following line passes data.restiming as parameter r to the addToBeacon function

https://github.com/akamai/boomerang/blob/c0cbec6da22c38733fef2a494104b4816b956fea/plugins/restiming.js#L1759-L1773

The addToBeacon function again checks for r.restiming, in the xhr_load event call this will be undefined as r is the restiming data and it will not have a field called restiming inside it

https://github.com/akamai/boomerang/blob/c0cbec6da22c38733fef2a494104b4816b956fea/plugins/restiming.js#L1693-L1699

This causes the restiming entries added to the beacon on xhr_load to be missed in the beacon