MongoDB Adapter fix and updates for scenarios (#1196)

* Updates for mongodb adapter; fix connection usage on cli

* Reduce the cycles for test w/ sporadic failures

* Removed redundant '-> string'

* Removed state tracking and cleanup

* Space cache capture and connection management

* Mongo client management w/ connection

* Remove unused getData()

* Removed debug entry no longer required

engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/uniform/StandardActivity.java

@@ -114,6 +114,7 @@ public class StandardActivity<R extends Op, S> extends SimpleActivity implements
                 adapters.put(driverName, adapter);
                 mappers.put(driverName, adapter.getOpMapper());
             }
+
             supersetConfig.assertValidConfig(activityDef.getParams().getStringStringMap());
 
             DriverAdapter adapter = adapters.get(driverName);