northd: Split out join_logical_ports. #4677

Job	Run time
linux rpm fedora	6m 50s
osx clang --disable-ssl	1m 55s
Prepare container	3m 27s
linux gcc --disable-ssl	2m 40s
linux clang --disable-ssl	2m 37s
linux gcc test -300	9m 39s
linux gcc test 301-600	6m 37s
linux gcc test 601- unstable	6m 55s
linux clang test sanitizers -300	12m 49s
linux clang test sanitizers 301-600	9m 6s
linux clang test sanitizers 601- unstable	11m 17s
linux gcc test -ljemalloc -300	9m 56s
linux gcc test -ljemalloc 301-600	6m 36s
linux gcc test -ljemalloc 601- unstable	6m 56s
linux gcc system-test-dpdk dpdk -100	17m 7s
linux gcc system-test-dpdk dpdk 101- unstable	14m 35s
linux gcc system-test-userspace -100	16m 3s
linux gcc system-test-userspace 101- unstable	13m 16s
linux gcc system-test -100	18m 36s
linux gcc system-test 101- unstable	17m 40s
linux clang system-test sanitizers -100	21m 10s
linux clang system-test sanitizers 101- unstable	19m 25s
linux x86 gcc --disable-ssl	2m 37s
	3h 57m 49s

Provide feedback