Allow multiple shareable SD Cards by using getShareableVolumes()

to get all the volumes that are shareable and allowing
sharing/unsharing for all of them rather than just the hardcoded
getExternalStorage calls.

Unmount immediately if PM is not updating and not an ASEC
mount. Change from Josh Stone.
Change-Id: Iaf1a7a4484deac373e1c1d7bf16d5f22ca49fd64

Only allow package manager for sdcard (packages aren't on
external card).

Change-Id: I0d148ea52dc1285905a9dd061d1ceedcfb761b52

Take out extra logging.

Change-Id: I6beb007700ef4be04c3eb273bbf2069c87b30011