northd: Don't SNAT reply packets on LBs with lb_force_snat_ip set. #3320

Job	Run time
dpdk gcc	4s
linux rpm fedora	6m 54s
Prepare container	2m 14s
osx clang --disable-ssl	2m 34s
linux gcc --disable-ssl	2m 19s
linux clang --disable-ssl	2m 14s
linux gcc test -300	9m 6s
linux gcc test 301-600	5m 47s
linux gcc test 601- unstable	5m 57s
linux clang test sanitizers -300	12m 0s
linux clang test sanitizers 301-600	8m 2s
linux clang test sanitizers 601- unstable	9m 48s
linux gcc test -ljemalloc -300	9m 15s
linux gcc test -ljemalloc 301-600	5m 48s
linux gcc test -ljemalloc 601- unstable	6m 9s
linux gcc system-test-dpdk dpdk -100	16m 3s
linux gcc system-test-dpdk dpdk 101- unstable	11m 0s
linux gcc system-test-userspace -100	15m 15s
linux gcc system-test-userspace 101- unstable	10m 5s
linux gcc system-test -100	17m 42s
linux gcc system-test 101- unstable	14m 4s
linux clang system-test sanitizers -100	19m 21s
linux clang system-test sanitizers 101- unstable	15m 45s
linux x86 gcc --disable-ssl	2m 10s
	3h 29m 36s

Provide feedback