Set both legacy and new UID routing attributes.

This should work on kernels that support either, as long as they
are older than 4.8.

Test: netd_integration_test passes with updated iproute and kernel
Test: netd_integration_test passes with existing iproute and kernel
Test: ConnectivityManagerTest and HostsideVpnTests pass on existing kernel
Test: ConnectivityManagerTest and HostsideVpnTests pass on updated kernel
Bug: 16355602
Change-Id: I9a2ef08ba2782587f43ea7d0609f5f07f6c3adb0