Clean up ASEC unmounting on physical storage.

When physical devices are unsafely removed, unmountAllAsecsInDir()
fails to find any ASECs, and leaves them all mounted, preventing the
rest of volume from going down.

Now we examine all ASEC containers, and remove when on external
storage, or when the storage media is no longer found.

Bug: 11175082
Change-Id: Iffa38ea43f7e5ad78b598374ebeb60a8727d99fd
4 files changed