northd: Use the same UUID for SB representation of Load_Balancer. #1429

Job	Run time
osx clang --disable-ssl	2m 25s
linux rpm fedora	7m 2s
Prepare container	3m 38s
linux gcc --disable-ssl	2m 38s
linux clang --disable-ssl	2m 41s
linux gcc test -300	9m 23s
linux gcc test 301-600	6m 34s
linux gcc test 601- unstable	6m 27s
linux clang test sanitizers -300	12m 21s
linux clang test sanitizers 301-600	9m 9s
linux clang test sanitizers 601- unstable	11m 7s
linux gcc test -ljemalloc -300	9m 53s
linux gcc test -ljemalloc 301-600	6m 36s
linux gcc test -ljemalloc 601- unstable	6m 50s
linux gcc system-test-dpdk dpdk -100	17m 34s
linux gcc system-test-dpdk dpdk 101- unstable	14m 19s
linux gcc system-test-userspace -100	16m 2s
linux gcc system-test-userspace 101- unstable	12m 57s
linux gcc system-test -100	18m 23s
linux gcc system-test 101- unstable	16m 52s
linux clang system-test sanitizers -100	20m 4s
linux clang system-test sanitizers 101- unstable	18m 28s
linux x86 gcc --disable-ssl	2m 32s
	3h 53m 55s

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