northd: fix missing port up when deleting and adding back an lsp #65

Job	Run time
osx clang --disable-ssl	4m 22s
dpdk gcc	4s
linux rpm fedora	6m 58s
linux gcc --disable-ssl	1m 49s
linux clang --disable-ssl	1m 55s
linux gcc test -300	8m 30s
linux gcc test 301-600	5m 20s
linux gcc test 601- unstable	4m 56s
linux clang test sanitizers -300	11m 15s
linux clang test sanitizers 301-600	7m 56s
linux clang test sanitizers 601- unstable	8m 44s
linux gcc test -ljemalloc -300	8m 47s
linux gcc test -ljemalloc 301-600	5m 38s
linux gcc test -ljemalloc 601- unstable	5m 3s
linux gcc system-test-dpdk dpdk -100	12m 39s
linux gcc system-test-dpdk dpdk 101- unstable	11m 55s
linux gcc system-test-userspace -100	11m 22s
linux gcc system-test-userspace 101- unstable	10m 56s
linux gcc system-test -100	14m 11s
linux gcc system-test 101- unstable	13m 20s
linux clang system-test sanitizers -100	15m 57s
linux clang system-test sanitizers 101- unstable	14m 11s
linux x86 gcc --disable-ssl	2m 0s
	3h 7m 48s

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