Disable proxy_arp at the end of test_proxy_arp (sonic-net#11977)

* Disable proxy_arp at the end of test_proxy_arp

* Add 2 seconds delay

Author: bingwang-ms

tests/arp/conftest.py

@@ -311,6 +311,9 @@ def proxy_arp_enabled(rand_selected_dut, config_facts):
     proxy_arp_del_cmd = 'sonic-db-cli CONFIG_DB HDEL "VLAN_INTERFACE|Vlan{}" proxy_arp'
     for vid, proxy_arp_val in list(old_proxy_arp_vals.items()):
         if 'enabled' not in proxy_arp_val:
+            # Disable proxy_arp explicitly
+            duthost.shell(proxy_arp_config_cmd.format(vid, 'disabled'))
+            time.sleep(2)
             # Delete the DB entry instead of using the config command to satisfy check_dut_health_status
             duthost.shell(proxy_arp_del_cmd.format(vid))