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
(cherry picked from commit c66995ad4d)

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;