Fix load balanced hairpin traffic for fragmented packets. #3256

Job	Run time
dpdk gcc	4s
linux rpm fedora	6m 38s
osx clang --disable-ssl	2m 14s
Prepare container	1m 56s
linux gcc --disable-ssl	2m 24s
linux clang --disable-ssl	2m 18s
linux gcc test -500	13m 53s
linux gcc test 501-1000	9m 58s
linux gcc test 1001-	5m 46s
linux clang test sanitizers -300	11m 5s
linux clang test sanitizers 301-600	14m 2s
linux clang test sanitizers 601-900	9m 14s
linux clang test sanitizers 901-1200	7m 47s
linux clang test sanitizers 1201-	7m 17s
linux gcc test -ljemalloc -500	14m 47s
linux gcc test -ljemalloc 501-1000	10m 40s
linux gcc test -ljemalloc 1001-	5m 59s
linux gcc system-test-dpdk dpdk -100	10m 55s
linux gcc system-test-dpdk dpdk 101-200	17m 34s
linux gcc system-test-dpdk dpdk 201-	19m 23s
linux gcc system-test-userspace -100	12m 6s
linux gcc system-test-userspace 101-200	15m 54s
linux gcc system-test-userspace 201-	17m 49s
linux gcc system-test -100	12m 45s
linux gcc system-test 101-200	18m 11s
linux gcc system-test 201-	25m 20s
linux clang system-test sanitizers -100	14m 37s
linux clang system-test sanitizers 101-200	20m 0s
linux clang system-test sanitizers 201-	27m 35s
linux x86 gcc --disable-ssl	2m 24s
	5h 40m 35s

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