Fix leftover multicast route issue

Author: MitchDrage

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/BridgeVifDriver.java

@@ -383,6 +383,11 @@ protected void deleteVnetBr(String brName, boolean deleteBr) {
             String scriptPath = null;
             if (cmdout != null && cmdout.contains("vxlan")) {
                 scriptPath = _modifyVxlanPath;
+                // Read the pif from the VXLAN device.
+                String vxlanPif = getVxlanPif(vNetId);
+                if (vxlanPif != null) {
+                    pName = vxlanPif;
+                }
             } else {
                 scriptPath = _modifyVlanPath;
             }
@@ -403,6 +408,10 @@ protected void deleteVnetBr(String brName, boolean deleteBr) {
         }
     }
 
+    protected String getVxlanPif(String vxlanId) {
+        return Script.runSimpleBashScript("ip -d link show vxlan" + vxlanId + " | grep -o 'dev [^ ]*' | cut -d' ' -f2");
+    }
+
     private void deleteExistingLinkLocalRouteTable(String linkLocalBr) {
         Script command = new Script("/bin/bash", _timeout);
         command.add("-c");