flush dns cache to get new dhcp lease on vm

Jenkinsfile

@@ -102,9 +102,12 @@ pipeline {
                     def targetHost = "${templateHost}.lan"
                     echo "Waiting for ${targetHost} (template hostname) to become available..."
 
-                    // Wait up to 3 minutes for the machine to respond to ping
-                    timeout(time: 3, unit: 'MINUTES') {
+                    // Wait up to 5 minutes for the machine to respond to ping
+                    timeout(time: 5, unit: 'MINUTES') {
                         waitUntil {
+                            // Flush DNS cache before each ping attempt
+                            sh(script: "sudo systemd-resolve --flush-caches 2>/dev/null || sudo resolvectl flush-caches 2>/dev/null || sudo nscd -i hosts 2>/dev/null || true", returnStatus: true)
+
                             def result = sh(
                                 script: "ping -c 1 ${targetHost} > /dev/null 2>&1",
                                 returnStatus: true