annex.dbdir fully working

Completes work started in e60766543f

I've verified that all the sqlite databases get stored in annex.dbdir
and are created successfully. If annex.dbdir does not exist, it will be
created; its parent directory must already exist though.

Sponsored-by: Dartmouth College's Datalad project

Database/Init.hs

@@ -36,11 +36,12 @@ initDb db migration = do
 	let tmpdb = tmpdbdir P.</> "db"
 	let tdb = T.pack (fromRawFilePath tmpdb)
 	gc <- Annex.getGitConfig
-	top <- case annexDbDir gc of
-		Just topdbdir -> pure $ parentDir $ topdbdir
-		Nothing -> parentDir <$> fromRepo gitAnnexDir
+	top <- parentDir <$> fromRepo gitAnnexDir
+	let tops = case annexDbDir gc of
+		Just topdbdir -> [top, parentDir topdbdir]
+		Nothing -> [top]
 	liftIO $ do
-		createDirectoryUnder [top] tmpdbdir
+		createDirectoryUnder tops tmpdbdir
 		runSqliteInfo (enableWAL tdb) migration
 	setAnnexDirPerm tmpdbdir
 	-- Work around sqlite bug that prevents it from honoring