SERVER-133108 added checks to CheckMetadataConsistency to validate the correctness of the shard metadata referring to non-existing databases. However, due to limitations in the CheckMetadataConsistency protocol between the primary nodes a the secondary replicas, we are not running this check on the secondaries.

The limitation is essentially due to the fact that the checkMetadataConsistencySecondaryParticipant command operates on a per-dbName or per-nss basis, so we cannot readily express that we want to check "non existent databases: