Fix update notification issue by moving two module level variables, _lastNotifiedBuildNumber and _lastInfoURLFetchTime, into their respective functions.
Also set default info URL fetch time to zero.
Move the code that performs "update notification check" from appReady to _beforeHTMLReady.
Remove underscore from all remaining _lastNotifiedBuildNumber instances.
Revert "Move the code that performs "update notification check" from appReady to _beforeHTMLReady."

This reverts commit 3c44e37c49727f2807c02cf02a39340861468ff5.
Merge pull request #7869 from adobe/rlim/update-notification-fix

Fix update notification issue