northd: Consolidate register usage in logical flows. #3356

Job	Run time
Prepare container	1m 3s
linux rpm fedora	6m 48s
osx clang --disable-ssl	2m 17s
linux gcc --disable-ssl	2m 38s
linux clang --disable-ssl	2m 39s
linux gcc test -300	9m 41s
linux gcc test 301-600	6m 39s
linux gcc test 601- unstable	7m 11s
linux clang test sanitizers -300	13m 29s
linux clang test sanitizers 301-600	9m 29s
linux clang test sanitizers 601- unstable	12m 30s
linux gcc test -ljemalloc -300	10m 28s
linux gcc test -ljemalloc 301-600	7m 15s
linux gcc test -ljemalloc 601- unstable	7m 15s
linux gcc system-test-dpdk dpdk -100	17m 21s
linux gcc system-test-dpdk dpdk 101- unstable	15m 13s
linux gcc system-test-userspace -100	15m 42s
linux gcc system-test-userspace 101- unstable	14m 8s
linux gcc system-test -100	18m 23s
linux gcc system-test 101- unstable	18m 27s
linux clang system-test sanitizers -100	20m 17s
linux clang system-test sanitizers 101- unstable	20m 15s
linux x86 gcc --disable-ssl	2m 33s
	4h 1m 41s

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