device: check connectivity on the IP interface

curl must bind to the interface that has IP configuration, not the
underlying device. Without this commit, connectivity check fails on
certain connection types (PPPoE, WWAN).

Fixes: 9d43869e47

src/devices/nm-device.c

@@ -1858,7 +1858,7 @@ nm_device_check_connectivity (NMDevice *self,
 
 		/* Kick off a real connectivity check. */
 		nm_connectivity_check_async (nm_connectivity_get (),
-		                             nm_device_get_iface (self),
+		                             nm_device_get_ip_iface (self),
 		                             concheck_cb,
 		                             data);
 		return;