More rows.Close() and rows.Err() (#3262)

Looks like we missed some `rows.Close()`

Even though `rows.Err()` is mostly not necessary, we should be more
consistent in the DB layer.

[skip ci]

federationapi/storage/postgres/notary_server_keys_metadata_table.go

@@ -151,7 +151,7 @@ func (s *notaryServerKeysMetadataStatements) SelectKeys(ctx context.Context, txn
 		}
 		results = append(results, sk)
 	}
-	return results, nil
+	return results, rows.Err()
 }
 
 func (s *notaryServerKeysMetadataStatements) DeleteOldJSONResponses(ctx context.Context, txn *sql.Tx) error {

federationapi/storage/postgres/queue_json_table.go

@@ -109,5 +109,5 @@ func (s *queueJSONStatements) SelectQueueJSON(
 		}
 		blobs[nid] = blob
 	}
-	return blobs, err
+	return blobs, rows.Err()
 }

federationapi/storage/postgres/relay_servers_table.go

@@ -110,7 +110,7 @@ func (s *relayServersStatements) SelectRelayServers(
 		}
 		result = append(result, spec.ServerName(relayServer))
 	}
-	return result, nil
+	return result, rows.Err()
 }
 
 func (s *relayServersStatements) DeleteRelayServers(

federationapi/storage/sqlite3/joined_hosts_table.go

@@ -216,5 +216,5 @@ func joinedHostsFromStmt(
 		})
 	}
 
-	return result, nil
+	return result, rows.Err()
 }

federationapi/storage/sqlite3/notary_server_keys_metadata_table.go

@@ -154,7 +154,7 @@ func (s *notaryServerKeysMetadataStatements) SelectKeys(ctx context.Context, txn
 		}
 		results = append(results, sk)
 	}
-	return results, nil
+	return results, rows.Err()
 }
 
 func (s *notaryServerKeysMetadataStatements) DeleteOldJSONResponses(ctx context.Context, txn *sql.Tx) error {

federationapi/storage/sqlite3/queue_json_table.go

@@ -135,5 +135,5 @@ func (s *queueJSONStatements) SelectQueueJSON(
 		}
 		blobs[nid] = blob
 	}
-	return blobs, err
+	return blobs, rows.Err()
 }

federationapi/storage/sqlite3/relay_servers_table.go

@@ -109,7 +109,7 @@ func (s *relayServersStatements) SelectRelayServers(
 		}
 		result = append(result, spec.ServerName(relayServer))
 	}
-	return result, nil
+	return result, rows.Err()
 }
 
 func (s *relayServersStatements) DeleteRelayServers(