lookForAlert fix

The <b>returnedFromExecuteAtom</b> variable was being used for multiple execution. This caused unnecessary calls to the proxy with <b>"au.alertIsPresent()"</b> as it was set to true by the first request and then set to false by the second. When the first then looked for the alert it was false. 

Changed it to be a map with a value for each request.

I ran the safari tests and they passed.