[arp] Allow use of discontiguous ports with ARP tests.

tests/arp/conftest.py

@@ -50,9 +50,27 @@ def intfs_for_test(duthosts, enum_rand_one_per_hwsku_frontend_hostname, enum_fro
         intf1 = ports_for_test[0]
         intf2 = ports_for_test[1]
     else:
-        # Select port index 0 & 1 two interfaces for testing
-        intf1 = ports[0]
-        intf2 = ports[1]
+        # Select first 2 ports that are admin 'up'
+        if duthost.is_multi_asic:
+            intf_status = duthost.show_interface(command='status', namespace=asic.namespace)['ansible_facts'][
+                'int_status']
+        else:
+            intf_status = duthost.show_interface(command='status')['ansible_facts']['int_status']
+
+        intf1 = None
+        intf2 = None
+        for a_port in ports:
+            if intf_status[a_port]['admin_state'] == 'up':
+                if intf1 is None:
+                    intf1 = a_port
+                elif intf2 is None:
+                    intf2 = a_port
+                else:
+                    break
+
+        if intf1 is None or intf2 is None:
+            pytest.skip("Not enough interfaces on this host/asic (%s/%s) to support test." % (duthost.hostname,
+                                                                                              asic.asic_index))
 
         po1 = get_po(mg_facts, intf1)
         po2 = get_po(mg_facts, intf2)