pingcheck fails on VPN without routes

[George Leslie-Waksman]

Certain OpenVPN connections do not register routes on the interface and use other mechanisms for managing traffic flow. These interfaces return an empty routes list.

when pingcheck initializes the interface, it registers the interface as NO_ROUTE: https://github.com/br101/pingcheck/blob/master/ping.c#L115

pingcheck assumes a ping will fail without actually checking.

However, a manual ping of the interface ping -I ... succeeds.

[Bruno Randolf]

should have been fixed with #8