Fix cost estimation in CStoreGetForeignPaths.
Fix cost estimation in CStoreGetForeignPaths.

Previously we also counted in standard attributes like tableoid, cmax, xmax, ... in CStoreGetForeignPaths, which resulted in under estimating the disk access cost. This change fixes that.

citusdata/cstore_fdw,olivermel/cstore_fdw,olivermel/cstore_fdw,olivermel/cstore_fdw,cpcloud/cstore_fdw,citusdata/cstore_fdw,cpcloud/cstore_fdw