conntrack: Fix flush not flushing all elements. #439

Job	Run time
dpdk gcc	2m 0s
osx clang --disable-ssl	2m 36s
linux rpm fedora	2m 25s
linux deb no dpdk	2m 34s
linux gcc --disable-ssl	13s
linux clang --disable-ssl	15s
linux gcc c99	18s
linux clang c99	13s
linux gcc test	1s
linux clang test asan	17s
linux clang test ubsan	18s
linux gcc test --enable-shared	1s
linux clang test --enable-shared	14s
linux gcc test dpdk	1s
linux clang test dpdk	25s
linux gcc test -ljemalloc	1s
linux clang test -ljemalloc	13s
linux gcc --enable-afxdp	13s
linux clang --enable-afxdp	23s
linux gcc dpdk --enable-shared	18s
linux clang dpdk --enable-shared	20s
linux gcc dpdk-shared	18s
linux clang dpdk-shared	18s
linux gcc dpdk-shared --enable-shared	16s
linux clang dpdk-shared --enable-shared	17s
linux gcc m32 --disable-ssl	1s
	14m 29s

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