northd: Add option to enable conntrack for router port #2582

Job	Run time
osx clang --disable-ssl	5m 54s
dpdk gcc	10s
linux rpm fedora	6m 47s
Prepare container	1m 6s
linux gcc --disable-ssl	2m 22s
linux clang --disable-ssl	2m 22s
linux gcc test -300	8m 56s
linux gcc test 301-600	5m 46s
linux gcc test 601- unstable	5m 32s
linux clang test sanitizers -300	11m 39s
linux clang test sanitizers 301-600	8m 24s
linux clang test sanitizers 601- unstable	9m 12s
linux gcc test -ljemalloc -300	9m 10s
linux gcc test -ljemalloc 301-600	6m 12s
linux gcc test -ljemalloc 601- unstable	5m 43s
linux gcc system-test-dpdk dpdk -100	13m 13s
linux gcc system-test-dpdk dpdk 101- unstable	12m 24s
linux gcc system-test-userspace -100	11m 46s
linux gcc system-test-userspace 101- unstable	11m 31s
linux gcc system-test -100	14m 32s
linux gcc system-test 101- unstable	12m 48s
linux clang system-test sanitizers -100	16m 20s
linux clang system-test sanitizers 101- unstable	14m 41s
linux x86 gcc --disable-ssl	2m 14s
	3h 18m 44s

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