Wait for uncrypt to finish before rebooting

Wait for uncrypt to finish before rebooting

/system/bin/uncrypt needs to be triggered to prepare the OTA package
before rebooting into the recovery. For larger packages, uncrypt may be
killed before it finishes the work after the timeout. Change to monitor
the uncrypt status and show the progress to user.

Needs matching changes in bootable/recovery/uncrypt, system/core and
external/sepolicy.

Also pick up the two NPE fixes in commits
9bb765448df43d41e0a3edb7de1d1641c9251c35 and
da3f63ffb87397943546a7c5c893ce98f2489df2.

Bug: 20012567
Bug: 20949086
(cherry picked from commit 90237f7beb55dae79cdcba5271f96be778573737)
Change-Id: Ibf2fc80032967e5f6cda3cd469005dd29665c87c