Use API RouteInfo constructor in VpnConfig

VpnConfig is planned to be outside of the connectivity module, so it
needs to use its public API and not private symbols.

Change the RouteInfo constructor to use the equivalent API version.

Bug: 174436414
Test: m
Change-Id: Iae264e9b50ec6e97ce39bd2bab6f22f5844bf270
1 file changed