ANDROID: GKI: set vfs-only exports into their own namespace

We have namespaces, so use them for all vfs-exported namespaces so that
filesystems can use them, but not anything else.

Bug: 157965270
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ic214d31360af5f1e025a176a61e346a8ec62a735