[strongSwan] commit 6b57790270fb07c579315c70ecce34f8ad9a4d63 is different when it comes to libcharon

[Jaehong Park]

Hi Martin.

6b57790270fb07c579315c70ecce34f8ad9a4d63

If a system uses routing metrics, we should honor them when doing (manual)
routing lookups for IKE. When enumerating routes, the kernel reports priorities
with the RTA_PRIORITY attribute, not RTA_METRICS. We prefer routes with a
lower priority value, and fall back to longest prefix match priorities if
the priority value is equal.

The logic of get_route  function in  /libcharon/plugins/kernel_netlink/kernel_netlink_net.c was ported to differently than it is described above.