Rewrite Jenkinsfile to new declarative syntax + parallel

Signed-off-by: Tibor Vass <tibor@docker.com>

Jenkinsfile

@@ -1,21 +1,37 @@
-wrappedNode(label: 'linux && x86_64', cleanWorkspace: true) {
-  timeout(time: 60, unit: 'MINUTES') {
-    stage "Git Checkout"
-    checkout scm
+pipeline {
+    agent {
+        label "linux && x86_64"
+    }
 
-    stage "Docker info"
-    sh "docker version"
-    sh "docker info"
+    options {
+        timeout(time: 60, unit: 'MINUTES')
+    }
 
-    stage("Run end-to-end test suite - Stable Engine")
-    sh "E2E_UNIQUE_ID=clie2e${BUILD_NUMBER} \
-      IMAGE_TAG=clie2e${BUILD_NUMBER} \
-      DOCKER_BUILDKIT=1 make -f docker.Makefile test-e2e"
-
-    stage("Run end-to-end test suite - 18.09 Engine")
-    sh "E2E_ENGINE_VERSION=18.09-dind \
-        E2E_UNIQUE_ID=clie2e${BUILD_NUMBER} \
-        IMAGE_TAG=clie2e${BUILD_NUMBER} \
-        DOCKER_BUILDKIT=1 make -f docker.Makefile test-e2e"
-  }
+    stages {
+        stage("Docker info") {
+            steps {
+                sh "docker version"
+                sh "docker info"
+            }
+        }
+        stage("end-to-end test suite") {
+            parallel {
+                stage("stable engine") {
+                    steps {
+                        sh "E2E_UNIQUE_ID=clie2e${BUILD_NUMBER} \
+                          IMAGE_TAG=clie2e${BUILD_NUMBER} \
+                          DOCKER_BUILDKIT=1 make -f docker.Makefile test-e2e"
+                    }
+                }
+                stage("18.09 engine") {
+                    steps {
+                        sh "E2E_ENGINE_VERSION=18.09-dind \
+                          E2E_UNIQUE_ID=clie2e${BUILD_NUMBER} \
+                          IMAGE_TAG=clie2e${BUILD_NUMBER} \
+                          DOCKER_BUILDKIT=1 make -f docker.Makefile test-e2e"
+                    }
+		}
+            }
+        }
+    }
 }