route-table: Allow parsing routes without nexthop. #6792

Job	Run time
dpdk gcc (ubuntu-24.04)	5s
libreswan (ubuntu-24.04)	5s
linux rpm fedora	2m 27s
build oss-fuzz fuzzers	1m 38s
linux deb no dpdk	2m 34s
osx clang --disable-ssl	1m 57s
clang-analyze-cache	11m 16s
linux gcc --disable-ssl	2m 31s
linux clang --disable-ssl	2m 6s
linux gcc c99	2m 15s
linux clang c99	6m 20s
linux gcc test	4m 3s
linux clang address,undefined test	2m 57s
linux gcc test --enable-shared	2m 16s
linux clang test --enable-shared	6m 14s
linux gcc check check-dpdk dpdk	1m 39s
linux clang check check-dpdk dpdk	4m 4s
linux gcc test -ljemalloc	2m 4s
linux clang test -ljemalloc	3m 12s
linux gcc --enable-afxdp	1m 39s
linux clang --enable-afxdp	4m 28s
linux gcc dpdk --enable-shared	2m 6s
linux clang dpdk --enable-shared	4m 14s
linux gcc dpdk-shared	3m 15s
linux clang dpdk-shared	5m 2s
linux gcc dpdk-shared --enable-shared	1m 57s
linux clang dpdk-shared --enable-shared	5m 7s
linux gcc m32 --disable-ssl	1m 42s
linux gcc check-ovsdb-cluster	3m 0s
linux gcc check-kernel -100	1m 43s
linux gcc check-kernel 100-	1m 42s
linux clang address,undefined check-kernel -100	2m 24s
linux clang address,undefined check-kernel 100-	3m 35s
linux gcc check-offloads -100	1m 46s
linux gcc check-offloads 100-	1m 40s
linux gcc dpdk check-system-userspace	1m 50s
linux clang address,undefined dpdk check-system-userspace	2m 30s
linux gcc dpdk check-system-tso	1m 57s
linux gcc dpdk check-afxdp	1m 50s
clang-analyze	4m 15s
	1h 57m 25s

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