Allow LR to send RAs with only link local Ipv6. #3298

Job	Run time
dpdk gcc	1m 33s
linux rpm fedora	6m 59s
osx clang --disable-ssl	2m 24s
Prepare container	2m 21s
linux gcc --disable-ssl	2m 20s
linux clang --disable-ssl	2m 18s
linux gcc test -300	9m 3s
linux gcc test 301-600	5m 42s
linux gcc test 601- unstable	5m 52s
linux clang test sanitizers -300	11m 34s
linux clang test sanitizers 301-600	8m 9s
linux clang test sanitizers 601- unstable	10m 5s
linux gcc test -ljemalloc -300	9m 35s
linux gcc test -ljemalloc 301-600	5m 41s
linux gcc test -ljemalloc 601- unstable	6m 8s
linux gcc system-test-dpdk dpdk -100	15m 58s
linux gcc system-test-dpdk dpdk 101- unstable	11m 16s
linux gcc system-test-userspace -100	15m 3s
linux gcc system-test-userspace 101- unstable	10m 18s
linux gcc system-test -100	17m 41s
linux gcc system-test 101- unstable	14m 20s
linux clang system-test sanitizers -100	19m 32s
linux clang system-test sanitizers 101- unstable	15m 54s
linux x86 gcc --disable-ssl	2m 20s
	3h 32m 6s

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