multi: rename chan DB Open method to OpenForTesting

funding/manager_test.go

@@ -427,10 +427,7 @@ func createTestFundingManager(t *testing.T, privKey *btcec.PrivateKey,
 	}
 
 	dbDir := filepath.Join(tempTestDir, "cdb")
-	fullDB, err := channeldb.Open(dbDir)
-	if err != nil {
-		return nil, err
-	}
+	fullDB := channeldb.OpenForTesting(t, dbDir)
 
 	cdb := fullDB.ChannelStateDB()