ANDROID: sdcardfs: Avoid setting GIDs outside of valid ranges

When setting up the ownership of files on the lower filesystem,
ensure that these values are in reasonable ranges for apps. If
they aren't, default to AID_MEDIA_RW

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 37516160
Change-Id: I0bec76a61ac72aff0b993ab1ad04be8382178a00