db.go: Don't skip some level
db.go: Don't skip some level

we get LevelTablesCounts = [65,34], seems L0 file num is 65
after reopen db,  LevelTablesCounts = [1,65,34]
the origin LevelTablesCounts should be [0,65,34]
if it skip some level, we have no any ideal what the Stat we get really
means

syndtr/goleveldb