node-neigh: Add retry for concurrent arping test case

The test became notoriously flaky. It seems that some goroutines were
lagging behind with the updates and they were overwritting the new MAC
addr entry with the obsolete.

To fix this, retry multiple times until the correct entry is found.

Signed-off-by: Martynas Pumputis <m@lambda.lt>

pkg/datapath/linux/node_linux_test.go

@@ -1188,23 +1188,28 @@ func (s *linuxPrivilegedIPv4OnlyTestSuite) TestArpPingHandling(c *check.C) {
 			c.Assert(err, check.IsNil)
 			return nil
 		})
+
 		// Check that MAC has been changed in the neigh table
-		time.Sleep(500 * time.Millisecond)
-		neighs, err = netlink.NeighList(veth0.Attrs().Index, netlink.FAMILY_V4)
-		c.Assert(err, check.IsNil)
-		found = false
-		for _, n := range neighs {
-			if n.IP.Equal(ip1) && n.State == netlink.NUD_PERMANENT {
-				c.Assert(n.HardwareAddr.String(), check.Equals, mac.String())
-				c.Assert(neighHwAddr(ip1.String()), check.Equals, mac.String())
-				c.Assert(neighRefCount(ip1.String()), check.Equals, 1)
-				found = true
-				break
+		var found bool
+		err := testutils.WaitUntilWithSleep(func() bool {
+			neighs, err = netlink.NeighList(veth0.Attrs().Index, netlink.FAMILY_V4)
+			c.Assert(err, check.IsNil)
+			found = false
+			for _, n := range neighs {
+				if n.IP.Equal(ip1) && n.State == netlink.NUD_PERMANENT &&
+					n.HardwareAddr.String() == mac.String() &&
+					neighHwAddr(ip1.String()) == mac.String() &&
+					neighRefCount(ip1.String()) == 1 {
+					found = true
+					return true
+				}
 			}
-		}
+			return false
+		}, 5*time.Second, 200*time.Millisecond)
+		c.Assert(err, check.IsNil)
 		c.Assert(found, check.Equals, true)
-
 	}
+
 	// Cleanup
 	close(done)
 	wg.Wait()