Add a per-boot-key policy reference, apply to per_boot

Includes changes picked from aosp/1119783
570d20d2ac875198416dff280b7a4b7adaacac81 in platform/system/core

Bug: 140882488
Test: Booted twice, checked logs to ensure encryption
    is different each time, adb created files in directory.
Cherry-Picked-From: ab3085004e35cff9517fcedb03317f3f1ac84cf9
Merged-In: I5c962edb316d160dd09c0df893912c6b257d7810
Change-Id: I5c962edb316d160dd09c0df893912c6b257d7810
2 files changed