northd: Preserve datapath tunnel id data in en_northd engine node. #4797

Job	Run time
linux rpm fedora	7m 14s
Prepare container	3m 24s
osx clang --disable-ssl	1m 58s
linux gcc --disable-ssl	2m 51s
linux clang --disable-ssl	2m 39s
linux gcc test -300	9m 36s
linux gcc test 301-600	6m 44s
linux gcc test 601- unstable	7m 9s
linux clang test sanitizers -300	13m 39s
linux clang test sanitizers 301-600	9m 30s
linux clang test sanitizers 601- unstable	12m 38s
linux gcc test -ljemalloc -300	10m 9s
linux gcc test -ljemalloc 301-600	7m 6s
linux gcc test -ljemalloc 601- unstable	7m 33s
linux gcc system-test-dpdk dpdk -100	16m 56s
linux gcc system-test-dpdk dpdk 101- unstable	15m 18s
linux gcc system-test-userspace -100	16m 6s
linux gcc system-test-userspace 101- unstable	14m 0s
linux gcc system-test -100	18m 18s
linux gcc system-test 101- unstable	18m 6s
linux clang system-test sanitizers -100	20m 29s
linux clang system-test sanitizers 101- unstable	20m 13s
linux x86 gcc --disable-ssl	2m 52s
	4h 4m 28s

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