route-table: Allow parsing routes without nexthop. #2633

Job	Run time
dpdk gcc (ubuntu-24.04)	9s
build oss-fuzz fuzzers	2m 56s
libreswan (ubuntu-24.04)	8s
linux deb no dpdk	5m 28s
linux rpm fedora	4m 19s
osx clang --disable-ssl	1m 44s
clang-analyze-cache	10m 59s
linux gcc --disable-ssl	2m 46s
linux clang --disable-ssl	2m 40s
linux gcc c99	2m 48s
linux clang c99	2m 46s
linux gcc test	8m 22s
linux clang address,undefined test	16m 36s
linux gcc test --enable-shared	11m 31s
linux clang test --enable-shared	11m 20s
linux gcc check check-dpdk dpdk	19m 55s
linux clang check check-dpdk dpdk	19m 49s
linux gcc test -ljemalloc	9m 5s
linux clang test -ljemalloc	9m 4s
linux gcc --enable-afxdp	3m 51s
linux clang --enable-afxdp	2m 44s
linux gcc dpdk --enable-shared	3m 59s
linux clang dpdk --enable-shared	3m 59s
linux gcc dpdk-shared	4m 55s
linux clang dpdk-shared	2m 56s
linux gcc dpdk-shared --enable-shared	3m 49s
linux clang dpdk-shared --enable-shared	3m 39s
linux gcc m32 --disable-ssl	2m 33s
linux gcc check-ovsdb-cluster	6m 39s
linux gcc check-kernel -100	10m 30s
linux gcc check-kernel 100-	17m 17s
linux clang address,undefined check-kernel -100	14m 9s
linux clang address,undefined check-kernel 100-	19m 44s
linux gcc check-offloads -100	9m 27s
linux gcc check-offloads 100-	12m 29s
linux gcc dpdk check-system-userspace	13m 45s
linux clang address,undefined dpdk check-system-userspace	17m 3s
linux gcc dpdk check-system-tso	13m 33s
linux gcc dpdk check-afxdp	12m 40s
clang-analyze	11m 26s
	5h 33m 32s

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