Close and destroy databases being left open during tests (#2806)

There were several tests in the Database suites that were failing to
close test Databases that had orderedChunkCaches in them (backed by
levelDBs). Close them.

I was ALSO failing to destroy the cache used in LocalDatabase
instances only while testing Pull(). That's cleared up now as well.

go/datas/database_test.go

@@ -111,12 +111,14 @@ func (suite *DatabaseSuite) TestCommitProperlyTracksRoot() {
 	id1, id2 := "testdataset", "othertestdataset"
 
 	db1 := suite.makeDb(suite.cs)
+	defer db1.Close()
 	ds1 := db1.GetDataset(id1)
 	ds1HeadVal := types.String("Commit value for " + id1)
 	ds1, err := db1.CommitValue(ds1, ds1HeadVal)
 	suite.NoError(err)
 
 	db2 := suite.makeDb(suite.cs)
+	defer db2.Close()
 	ds2 := db2.GetDataset(id2)
 	db2HeadVal := types.String("Commit value for " + id2)
 	ds2, err = db2.CommitValue(ds2, db2HeadVal)
@@ -187,9 +189,9 @@ func (suite *DatabaseSuite) TestDatabaseCommit() {
 
 	// Get a fresh database, and verify that both datasets are present
 	newDB := suite.makeDb(suite.cs)
+	defer newDB.Close()
 	datasets2 := newDB.Datasets()
 	suite.Equal(uint64(2), datasets2.Len())
-	newDB.Close()
 }
 
 func newOpts(parents ...types.Value) CommitOptions {
@@ -279,11 +281,11 @@ func (suite *DatabaseSuite) TestDatabaseDelete() {
 
 	// Get a fresh database, and verify that only ds1 is present
 	newDB := suite.makeDb(suite.cs)
+	defer newDB.Close()
 	datasets = newDB.Datasets()
 	suite.Equal(uint64(1), datasets.Len())
 	_, present = newDB.GetDataset(datasetID2).MaybeHeadRef()
 	suite.True(present, "Dataset %s should be present", datasetID2)
-	newDB.Close()
 }
 
 type waitDuringUpdateRootChunkStore struct {
@@ -314,6 +316,7 @@ func (suite *DatabaseSuite) TestCommitWithConcurrentChunkStoreUse() {
 	// Craft DB that will allow me to move the backing ChunkStore while suite.db isn't looking
 	w := &waitDuringUpdateRootChunkStore{suite.cs, nil}
 	db := suite.makeDb(w)
+	defer db.Close()
 
 	// Concurrent change, but to some other dataset. This shouldn't stop changes to ds1.
 	// ds1: |a| <- |b|
@@ -368,6 +371,7 @@ func (suite *DatabaseSuite) TestDeleteWithConcurrentChunkStoreUse() {
 	// Craft DB that will allow me to move the backing ChunkStore while suite.db isn't looking
 	w := &waitDuringUpdateRootChunkStore{suite.cs, nil}
 	db := suite.makeDb(w)
+	defer db.Close()
 
 	// Concurrent change, to move root out from under my feet:
 	// ds1: |a| <- |b| <- |e|

go/datas/local_batch_store.go

@@ -127,6 +127,11 @@ func (lbs *localBatchStore) FlushAndDestroyWithoutClose() {
 	lbs.unwrittenPuts.Destroy()
 }
 
+// Destroy blows away lbs' cache of unwritten chunks without flushing. Used when the owning Database is closing and it isn't semantically correct to flush.
+func (lbs *localBatchStore) Destroy() {
+	lbs.unwrittenPuts.Destroy()
+}
+
 // Close is supposed to close the underlying ChunkStore, but the only place localBatchStore is currently used wants to keep the underlying ChunkStore open after it's done with lbs. Hence, the above method and the panic() here.
 func (lbs *localBatchStore) Close() error {
 	panic("Unreached")

go/datas/local_database.go

@@ -67,3 +67,11 @@ func (ldb *LocalDatabase) validatingBatchStore() types.BatchStore {
 	}
 	return ldb.vbs
 }
+
+func (ldb *LocalDatabase) Close() error {
+	if ldb.vbs != nil {
+		ldb.vbs.Destroy()
+		ldb.vbs = nil
+	}
+	return ldb.databaseCommon.Close()
+}