channeldb: move makeTestDB out of test to make it available for other tests

This commit moves makeTestDB to db.go and exports it so that we'll be
able to use this function in other unit tests to make them testable with
etcd if needed.

channeldb/meta_test.go

@@ -15,7 +15,7 @@ import (
 func applyMigration(t *testing.T, beforeMigration, afterMigration func(d *DB),
 	migrationFunc migration, shouldFail bool, dryRun bool) {
 
-	cdb, cleanUp, err := makeTestDB()
+	cdb, cleanUp, err := MakeTestDB()
 	defer cleanUp()
 	if err != nil {
 		t.Fatal(err)
@@ -86,7 +86,7 @@ func applyMigration(t *testing.T, beforeMigration, afterMigration func(d *DB),
 func TestVersionFetchPut(t *testing.T) {
 	t.Parallel()
 
-	db, cleanUp, err := makeTestDB()
+	db, cleanUp, err := MakeTestDB()
 	defer cleanUp()
 	if err != nil {
 		t.Fatal(err)