Prepare debian changelog for 3.0.21
Prepare debian changelog for 3.0.21

mshuler/cassandra,pauloricardomg/cassandra,thelastpickle/cassandra,jrwest/cassandra,pauloricardomg/cassandra,krummas/cassandra,snazy/cassandra,adejanovski/cassandra,blerer/cassandra,belliottsmith/cassandra,beobal/cassandra,belliottsmith/cassandra,adejanovski/cassandra,jrwest/cassandra,blambov/cassandra,pauloricardomg/cassandra,snazy/cassandra,szhou1234/cassandra,mike-tr-adamson/cassandra,mshuler/cassandra,instaclustr/cassandra,snazy/cassandra,scylladb/scylla-tools-java,jrwest/cassandra,driftx/cassandra,michaelsembwever/cassandra,tjake/cassandra,pauloricardomg/cassandra,szhou1234/cassandra,instaclustr/cassandra,szhou1234/cassandra,bdeggleston/cassandra,mshuler/cassandra,blambov/cassandra,driftx/cassandra,beobal/cassandra,bdeggleston/cassandra,scylladb/scylla-tools-java,scylladb/scylla-tools-java,tjake/cassandra,blerer/cassandra,thelastpickle/cassandra,adelapena/cassandra,krummas/cassandra,beobal/cassandra,michaelsembwever/cassandra,strapdata/cassandra,thelastpickle/cassandra,blerer/cassandra,blerer/cassandra,jrwest/cassandra,strapdata/cassandra,belliottsmith/cassandra,blambov/cassandra,tjake/cassandra,mike-tr-adamson/cassandra,strapdata/cassandra,apache/cassandra,adelapena/cassandra,apache/cassandra,snazy/cassandra,mike-tr-adamson/cassandra,adelapena/cassandra,apache/cassandra,bdeggleston/cassandra,mike-tr-adamson/cassandra,adejanovski/cassandra,strapdata/cassandra,driftx/cassandra,tjake/cassandra,michaelsembwever/cassandra,driftx/cassandra,instaclustr/cassandra,beobal/cassandra,apache/cassandra,blambov/cassandra,instaclustr/cassandra,thelastpickle/cassandra,szhou1234/cassandra,belliottsmith/cassandra,krummas/cassandra,krummas/cassandra,michaelsembwever/cassandra,scylladb/scylla-tools-java,mshuler/cassandra,bdeggleston/cassandra,adelapena/cassandra