SERVER-42040 added logging of commits of registerChanges at the same log level as rollbacks of registerChanges. Since commits occur far more frequently than rollbacks, the log level of commits should be bumped to 3 instead of 2.
Additionally, SERVER-42040 increased the overall log level in the replica_sets_initsync_jscore_passthrough testing suite to 2. We should instead increase only the log level of the storage component to 2.