tests: net: vlan: Fix the socket API usage

The tests should use zsock_ APIs after the commit
0512e7ffaead7eeb2d3599cc71e439180e221e4a

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>
diff --git a/tests/net/vlan/src/main.c b/tests/net/vlan/src/main.c
index 5d53bfd..b9eada2 100644
--- a/tests/net/vlan/src/main.c
+++ b/tests/net/vlan/src/main.c
@@ -794,9 +794,9 @@
 	ret = add_neighbor(iface, &server_addr.sin6_addr);
 	zassert_true(ret, "Cannot add neighbor");
 
-	ret = bind(server_sock,
-		   (struct sockaddr *)&server_addr,
-		   sizeof(server_addr));
+	ret = zsock_bind(server_sock,
+			 (struct sockaddr *)&server_addr,
+			 sizeof(server_addr));
 	zassert_equal(ret, 0, "bind failed");
 
 	test_started = true;
@@ -808,9 +808,9 @@
 			     (struct sockaddr *)&server_addr,
 			     sizeof(server_addr));
 
-	ret = close(client_sock);
+	ret = zsock_close(client_sock);
 	zassert_equal(ret, 0, "close failed");
-	ret = close(server_sock);
+	ret = zsock_close(server_sock);
 	zassert_equal(ret, 0, "close failed");
 }