Destroy DSU metadata encryption key when wiping an installation

Call IVold::destroyDsuMetadataKey() to destroy the old key.
This ensures that wiping and reinstalling a DSU system would generate
different metadata encryption keys, albeit using the same key dir.

Bug: 168571434
Test: 1. Install a DSU system.
  2. Boot the DSU system and reboot back to the host system.
  3. Wipe the DSU installation.
  4. DSU metadata key dir /metadata/vold/metadata_encryption/dsu/dsu is
     destroyed.
Change-Id: I5b66c6ac440f857a7bb22341d5dc70480a4075b2
2 files changed