ipsec: enable input features on tunnels

ipsec: enable input features on tunnels

Make the ipsec[46]-tun-input nodes siblings of device-input so that
input features can be enabled on them. Register ipsec-tun for feature
updates. When a feature is enabled on the device-input arc and the
ifindex is an IPSec tunnel, change the end node of the arc for that
ifindex to be the appropriate ESP decrypt node. Set a flag on the
tunnel to indicate that the feature arc should be started for packets
input on the tunnel.

Test input policing on ESP IPSec tunnels.

Type: improvement
Signed-off-by: Brian Russell <brian@graphiant.com>
Change-Id: I3b9f047e5e737f3ea4c58fc82cd3c15700b6f9f7