init sets keystore.boot_level, keystore reads

Bug: 176450483
Test: init can set, and keystore2 read, keystore.boot_level
Test: `adb shell getprop -Z | grep boot_level` returns
      [keystore.boot_level]: [u:object_r:keystore_listen_prop:s0]
Change-Id: Iedb37db19e9153995800fc97de6ee8c536179caa
4 files changed