Handle 'sk' being NULL in UID-based routing.

Bug: 15413527
Change-Id: If33bebb7b52c0ebfa8dac2452607bce0c2b0faa0
Signed-off-by: Sreeram Ramachandran <sreeram@google.com>

Conflicts:
	include/net/route.h

	modified:   include/net/route.h
Cherry pick test and Kernel testing for LP
net: core: Support UID-based routing.

This contains the following commits:

1. 0149763 net: core: Add a UID range to fib rules.
2. 1650474 net: core: Use the socket UID in routing lookups.
3. 0b16771 net: ipv4: Add the UID to the route cache.
4. ee058f1 net: core: Add a RTA_UID attribute to routes.
    This is so that userspace can do per-UID route lookups.

Bug: 15413527
Change-Id: I1285474c6734614d3bda6f61d88dfe89a4af7892
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

Conflicts:
	include/net/flow.h
	include/net/ip.h
	include/net/route.h
	net/ipv4/raw.c
	net/ipv6/ping.c
Conflicts caused by patching in the wrong direction, be sure to start at the first patch :(