From PM-3857, we have found a gap in unit testing where a statistic inside a function has been incremented. In current state, whenever a WT_CONN_STAT_INCR is invoked, we ignore it as statistics are not enabled as part of Wiredtiger open. In WiredTiger statistics are incremented when certain code paths are hit, these would be valuable for unit tests. Unit tests would be able to assert that certain statistics are incrememnented when expected code paths have been set.

This ticket involves improving the mockConnection class by also initailizing the statistic framework.