Removed a function local static in SeedCleanerByHitPosition::good

The static analyzer complained about a non-const static being used in SeedCleanerByHitPosition::good.
The static was an instance of RecHitComparatorByPostion which is a class with no member data. Therefore
making it static didn't do anything useful. Removed the static and made it const just to make its use
clear.
Merge pull request #1902 from Dr15Jones/removedStaticInSeedCleanerByHitPosition

Multithreading fixes -- Removed a function local static in SeedCleanerByHitPosition::good