speed up keys database writes

There seems to be no reason to check the time here. I think it was
inherited from code in Database.Fsck, which does have a reason to commit
every few minutes. Removing that syscall speeds up a git-annex init
in a repo with 100000 annexed files by about 3 seconds.

Sponsored-by: Dartmouth College's Datalad project

Database/Fsck.hs

@@ -88,7 +88,9 @@ addDb :: FsckHandle -> Key -> IO ()
 addDb (FsckHandle h _) k = H.queueDb h checkcommit $
 	void $ insertUnique $ Fscked k
   where
-	-- commit queue after 1000 files or 5 minutes, whichever comes first
+	-- Commit queue after 1000 changes or 5 minutes, whichever comes first.
+	-- The time based commit allows for an incremental fsck to be
+	-- interrupted and not lose much work.
 	checkcommit sz lastcommittime
 		| sz > 1000 = return True
 		| otherwise = do