[MONDRIAN-1776] PhysStatistic.getRelationCardinality() was using an inva...

...lid instanceof comparison, checking whether the PhysRelation was of type MondrianDef.Table,
when RolapSchema.PhysTable was intended.  Because of this all cardinality checks would use the stats provider's .getQueryCardinality() method for making the determination, which should be accurate but may be more costly.

This was also causing issues with mongolap since the Mongo stats provider does not implement support for .getQueryCardinality().