selftests: bonding: add delay before each xvlan_over_bond connectivity check

Jakub reported increased flakiness in bond_macvlan_ipvlan.sh on regular kernel, while the tests consistently pass on a debug kernel. This suggests a timing-sensitive issue.

To mitigate this, introduce a short sleep before each xvlan_over_bond connectivity check. The delay helps ensure neighbor and route cache have fully converged before verifying connectivity.

The sleep interval is kept minimal since check_connection() is invoked nearly 100 times during the test.

---
 .../testing/selftests/drivers/net/bonding/bond_macvlan_ipvlan.sh | 1 +
 1 file changed, 1 insertion(+)

index c4711272fe45..559f300f965a 100755
@@ -30,6 +30,7 @@ check_connection()
 	local message=${3}
 	RET=0
 
+	sleep 0.25
 	ip netns exec ${ns} ping ${target} -c 4 -i 0.1 &>/dev/null
 	check_err $? "ping failed"
 	log_test "${bond_mode}/${xvlan_type}_${xvlan_mode}: ${message}"

2.50.1