Securely encrypt the master key

Move functionality from init into vold so we can use
vold to manage key encryption

This is one of four changes to enable this functionality:
  https://android-review.googlesource.com/#/c/144586/
  https://android-review.googlesource.com/#/c/144663/
  https://android-review.googlesource.com/#/c/144672/
  https://android-review.googlesource.com/#/c/144673/

Bug: 18151196
Change-Id: I4a1c79d27f0d225a9ce4ac21653279919f75c991
10 files changed