SELinux: Add a new peer class and permissions to the Flask definitions

Add additional Flask definitions to support the new "peer" object class and
additional permissions to the netif, node, and packet object classes.  Also,
bring the kernel Flask definitions up to date with the Fedora SELinux policies
by adding the "flow_in" and "flow_out" permissions to the "packet" class.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>