AndroidSystemCore

When packages change, existing package-specific directories may have
gained/lost a UID mapping, so we need to update the permissions for
any in-memory nodes.

This allows an app to deliver data for another package before that
package is installed, which is the typical pattern of how OBB files
are delivered.

Also fix bug by re-deriving permissions when files are moved.

Bug: 25399427
Change-Id: I06f38a24ad7dee5f5099ba81429aef03208e5683