Further optimize displayGlobalPage()

The checks in canBeGlobal() are quick and not worth the overhead
of caching in the MapCacheLRU.

We already validate the username in canBeGlobal(), so no need to
do it again in displayGlobalPage().

Bug: 70585
Change-Id: If283c479fa6e06c6f1eece722f41918eadce2ebb