northd: Don't generate IPv6 prefix delegation flows if not configured. #3268

Job	Run time
Prepare container	1m 13s
linux rpm fedora	7m 7s
osx clang --disable-ssl	2m 34s
linux gcc --disable-ssl	2m 47s
linux clang --disable-ssl	2m 48s
linux gcc test -300	9m 17s
linux gcc test 301-600	6m 20s
linux gcc test 601- unstable	6m 42s
linux clang test sanitizers -300	12m 40s
linux clang test sanitizers 301-600	9m 11s
linux clang test sanitizers 601- unstable	11m 7s
linux gcc test -ljemalloc -300	9m 56s
linux gcc test -ljemalloc 301-600	6m 43s
linux gcc test -ljemalloc 601- unstable	6m 46s
linux gcc system-test-dpdk dpdk -100	16m 52s
linux gcc system-test-dpdk dpdk 101- unstable	14m 18s
linux gcc system-test-userspace -100	15m 59s
linux gcc system-test-userspace 101- unstable	13m 14s
linux gcc system-test -100	18m 18s
linux gcc system-test 101- unstable	17m 29s
linux clang system-test sanitizers -100	20m 25s
linux clang system-test sanitizers 101- unstable	19m 15s
linux x86 gcc --disable-ssl	2m 47s
	3h 53m 48s

Provide feedback