settings: ignore incompatible connections when looking for existing ones

beb18050 made this code run for all devices instead of just ethernet
devices, which means any kind of connection gets compared to any
device.  But only compatible connections should be considered.

(cherry picked from commit 77d01c9094)

src/settings/nm-settings.c

@@ -1592,6 +1592,9 @@ have_connection_for_device (NMSettings *self, NMDevice *device)
 		NMConnection *connection = NM_CONNECTION (data);
 		const char *ctype, *iface;
 
+		if (!nm_device_check_connection_compatible (device, connection))
+			continue;
+
 		s_con = nm_connection_get_setting_connection (connection);
 
 		iface = nm_setting_connection_get_interface_name (s_con);