Update code snippets with retry step (#1556)

Author: Vlatombe

src/main/resources/org/csanchez/jenkins/plugins/kubernetes/pipeline/samples/declarative.groovy

@@ -27,6 +27,7 @@ spec:
             //     sh 'hostname'
             // }
             defaultContainer 'shell'
+            retries 2
         }
     }
     stages {

src/main/resources/org/csanchez/jenkins/plugins/kubernetes/pipeline/samples/maven.groovy

@@ -7,15 +7,17 @@ kind: Pod
 spec:
   containers:
   - name: maven
-    image: maven:3.6.3-jdk-8
+    # In a real Jenkinsfile, it is recommended to pin to a specific version and use Dependabot or Renovate to bump it.
+    image: maven:latest
     command:
     - sleep
     args:
     - infinity
 ''') {
-    node(POD_LABEL) {
-        // or, for example: git 'https://github.com/jglick/simple-maven-project-with-tests'
-        writeFile file: 'pom.xml', text: '''
+    retry(count: 2, conditions: [kubernetesAgent(), nonresumable()]) {
+        node(POD_LABEL) {
+            // or, for example: git 'https://github.com/jglick/simple-maven-project-with-tests'
+            writeFile file: 'pom.xml', text: '''
 <project xmlns="http://maven.apache.org/POM/4.0.0">
     <modelVersion>4.0.0</modelVersion>
     <groupId>sample</groupId>
@@ -45,17 +47,18 @@ spec:
     </properties>
 </project>
         '''
-        writeFile file: 'src/test/java/sample/SomeTest.java', text: '''
+            writeFile file: 'src/test/java/sample/SomeTest.java', text: '''
 package sample;
 public class SomeTest {
     @org.junit.Test
     public void checks() {}
 }
         '''
-        container('maven') {
-            sh 'mvn -B -ntp -Dmaven.test.failure.ignore verify'
+            container('maven') {
+                sh 'mvn -B -ntp -Dmaven.test.failure.ignore verify'
+            }
+            junit '**/target/surefire-reports/TEST-*.xml'
+            archiveArtifacts '**/target/*.jar'
         }
-        junit '**/target/surefire-reports/TEST-*.xml'
-        archiveArtifacts '**/target/*.jar'
     }
 }

src/main/resources/org/csanchez/jenkins/plugins/kubernetes/pipeline/samples/windows.groovy

@@ -19,9 +19,11 @@ spec:
   nodeSelector:
     kubernetes.io/os: windows
 ''') {
-    node(POD_LABEL) {
-        container('shell') {
-            powershell 'Get-ChildItem Env: | Sort Name'
+    retry(count: 2, conditions: [kubernetesAgent(), nonresumable()]) {
+        node(POD_LABEL) {
+            container('shell') {
+                powershell 'Get-ChildItem Env: | Sort Name'
+            }
         }
     }
 }