Fix duplicate property DruidDatasource.database (#2348)
Fix duplicate property DruidDatasource.database (#2348)

fixes https://github.com/airbnb/superset/issues/2347
robert-digit/superset,massgov/incubator-superset,mistercrunch/panoramix,FrederichCheng/incubator-superset,FrederichCheng/incubator-superset,robert-digit/superset,SingTel-DataCo/incubator-superset,timifasubaa/incubator-superset,BRD-CD/superset,FrederichCheng/incubator-superset,nekia/incubator-superset-dev,FrederichCheng/incubator-superset,SingTel-DataCo/incubator-superset,airbnb/superset,apache/incubator-superset,alanmcruickshank/superset-dev,airbnb/caravel,zhouyao1994/incubator-superset,airbnb/superset,massgov/incubator-superset,nekia/incubator-superset-dev,airbnb/caravel,alanmcruickshank/superset-dev,zhouyao1994/incubator-superset,dmigo/incubator-superset,SingTel-DataCo/incubator-superset,airbnb/superset,dmigo/incubator-superset,asdf2014/superset,SingTel-DataCo/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,BRD-CD/superset,ArijanaBrlek/superset,timifasubaa/incubator-superset,nekia/incubator-superset-dev,nekia/incubator-superset-dev,apache/incubator-superset,timifasubaa/incubator-superset,apache/incubator-superset,asdf2014/superset,ArijanaBrlek/superset,dmigo/incubator-superset,mistercrunch/panoramix,timifasubaa/incubator-superset,airbnb/caravel,asdf2014/superset,massgov/incubator-superset,robert-digit/superset,zhouyao1994/incubator-superset,ArijanaBrlek/superset,apache/incubator-superset,mistercrunch/panoramix,alanmcruickshank/superset-dev,asdf2014/superset,alanmcruickshank/superset-dev,zhouyao1994/incubator-superset,BRD-CD/superset,BRD-CD/superset,massgov/incubator-superset,robert-digit/superset,dmigo/incubator-superset,apache/incubator-superset,ArijanaBrlek/superset,mistercrunch/panoramix,airbnb/caravel