Avoid the following test failure within network-sandbox:
    tests/cksuite-all-netns.c:335:F:Core:route_1:0: command(system("ip -d link set v1 up")) has unexpected positive return code 512
--- a/tests/nl-test-util.c
+++ b/tests/nl-test-util.c
@@ -780,12 +780,7 @@ bool _nltst_in_ci(void)
 
 bool _nltst_has_iproute2(void)
 {
-	static int has = -1;
-
-	if (has == -1)
-		has = (system("ip link &>/dev/null") == 0);
-
-	return has;
+	return false;
 }
 
 bool _nltst_skip_no_iproute2(const char *msg)