Correct debugging of accountsForUser binder cache

Bug: 140788621

Replaced the default result comparison so that two results can be compared
for value equality.  This code is only exercised with VERIFY is set true
in PropertyInvalidatedCache (this is a compile-time flag).

Test: Created a special build that sets VERIFY to true; verified that the
binder cache does not detect any inconsistent results.  Further modified
the build to generate inconsistencies; verified that the new code does,
in fact, detect true inconsistencies.

Change-Id: I48080cd3109b96159f711bd2d84a69530450c2c8