selftests: net: use slowwait to stabilize vrf_route_leaking test

The vrf_route_leaking test occasionally fails due to connectivity issues
in our testing environment. A sample failure message shows that the ping
check fails intermittently

  PING 2001:db8:16:2::2 (2001:db8:16:2::2) 56 data bytes

  --- 2001:db8:16:2::2 ping statistics ---
  1 packets transmitted, 0 received, 100% packet loss, time 0ms

  TEST: Basic IPv6 connectivity                                       [FAIL]

This is likely due to insufficient wait time on slower machines. To address
this, switch to using slowwait, which provides a longer and more reliable
wait for setup completion.

Before this change, the test failed 3 out of 10 times. After applying this
fix, the test was run 30 times without any failure.

Signed-off-by: Hangbin Liu <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: liuhangbin

tools/testing/selftests/net/vrf_route_leaking.sh

@@ -275,7 +275,7 @@ setup_sym()
 
 
 	# Wait for ip config to settle
-	sleep 2
+	slowwait 5 ip netns exec $h1 "${ping6}" -c1 -w1 ${H2_N2_IP6} >/dev/null 2>&1
 }
 
 setup_asym()
@@ -370,7 +370,7 @@ setup_asym()
 	ip -netns $r2 -6 addr add dev eth1 ${R2_N2_IP6}/64 nodad
 
 	# Wait for ip config to settle
-	sleep 2
+	slowwait 5 ip netns exec $h1 "${ping6}" -c1 -w1 ${H2_N2_IP6} >/dev/null 2>&1
 }
 
 check_connectivity()