Fix drillPick logic to work with show instance attributes.
Fix drillPick logic to work with show instance attributes.

Partially fixes #2442 (except in cases where there is no show attribute).

jason-crow/cesium,emackey/cesium,geoscan/cesium,CesiumGS/cesium,hodbauer/cesium,emackey/cesium,wallw-bits/cesium,AnimatedRNG/cesium,emackey/cesium,YonatanKra/cesium,aelatgt/cesium,progsung/cesium,kaktus40/cesium,AnimatedRNG/cesium,wallw-bits/cesium,oterral/cesium,CesiumGS/cesium,likangning93/cesium,aelatgt/cesium,esraerik/cesium,ggetz/cesium,soceur/cesium,oterral/cesium,AnalyticalGraphicsInc/cesium,oterral/cesium,AnimatedRNG/cesium,CesiumGS/cesium,likangning93/cesium,NaderCHASER/cesium,kiselev-dv/cesium,kiselev-dv/cesium,likangning93/cesium,progsung/cesium,AnimatedRNG/cesium,josh-bernstein/cesium,NaderCHASER/cesium,josh-bernstein/cesium,AnalyticalGraphicsInc/cesium,aelatgt/cesium,aelatgt/cesium,soceur/cesium,jasonbeverage/cesium,YonatanKra/cesium,kaktus40/cesium,ggetz/cesium,jason-crow/cesium,ggetz/cesium,kiselev-dv/cesium,denverpierce/cesium,soceur/cesium,geoscan/cesium,omh1280/cesium,esraerik/cesium,denverpierce/cesium,likangning93/cesium,wallw-bits/cesium,YonatanKra/cesium,YonatanKra/cesium,kiselev-dv/cesium,CesiumGS/cesium,likangning93/cesium,esraerik/cesium,denverpierce/cesium,omh1280/cesium,esraerik/cesium,hodbauer/cesium,jason-crow/cesium,emackey/cesium,NaderCHASER/cesium,jason-crow/cesium,wallw-bits/cesium,omh1280/cesium,hodbauer/cesium,denverpierce/cesium,omh1280/cesium,ggetz/cesium,CesiumGS/cesium,jasonbeverage/cesium