Description:
------------
When fixing Bug 65838 [Session unexpectedly expires], a fix was taken to calculate the expiration time as the difference between the "last used" and "now".  Previously, it was calculated between "added" and "now".  Calculating from "last used" seemed more in-line with the existing comments in the code, as well providing the expected behavior (LRU cache).

I can now see that the place where this fix was made affects *all* of the WinCache caches (File, User, Session), each of which may have a different expectation of when items in the cache should expire.


Expected result:
----------------
File & Session cache should calculate TTL from last use (pvalue->use_ticks).
User cache should calculate TTL from creation (pvalue->add_ticks).

Actual result:
--------------
After fix 65838 applied, User cache calculates TTL from last use.  This breaks the expectation that User cache entries will strictly expire from the time the entry was added to the cache.