vold: Add support for unencrypted persistent info

In order to display the correct language, timezone, airplane
mode and other settings on the decrypt screen, a copy of those
settings needs to be stored unencrypted so the framework can
query them.  This adds support to vold to store up to 32
property like key/value pairs that are not encrypted.

Change-Id: Id5c936d2c57d46ed5cff9325d92ba1e8d2ec8972
4 files changed