fstab: use auto mount point for voldmanaged volumes

Change-Id: I4dcb00c419c3dc0d1bca6c5d6b71d47f03ecbc8f
fstab: actually use auto mount point for usbdisk

* typo fix, s/audo/auto/

Change-Id: Ibf02dbb0e4262c3192df0d974b210a3c716af568