Allow packages.list access with new GID.

The FUSE daemon is using packages.list to map from package name to
appId after it drops permissions, so create a new "package_info" GID
to grant read access.

Also switches FileUtils to use Libcore.os.

Change-Id: I9451ca4e90e8a985526805c6df0888a244a1db36
5 files changed