Fix for jsr107tck-40 issue: make CacheExpiryTest counting getExpiry calls less rigid

For details, see https://github.com/jsr107/jsr107tck/issues/40

To summarize, relaxed constraint to only test a minimum number of getExpiry calls (required by spec) but removed
constraint that it was an error if more than the minimum number of calls to getExpiry methods are made.