Instrumentation to report when alterImpressionData is not found

This is to help diagnose a possible race condition, where the script tags
injected into the DOM by insertBanner may be executed asynchronously, and
the conditional which checks for alterImpressionData is run before the
function is created by banner javascript.

Change-Id: Ifef70bc81205da788abf7be1e87d2b14cc61271b