WIP: Add docker-based integ tests on Jenkins

Jenkinsfile

@@ -1 +1,39 @@
+def LOGSTASH_DOCKER_IMAGE="logstash/logstash"
+def LOGSTASH_DOCKER_REGISTRY="docker.elastic.co"
+def LOGSTASH_DOCKER_VERSION="5.4.1" 
+def LOGSTASH_DOCKER_ENV="XPACK_MONITORING_ENABLED=false"
+def LOGSTASH_PIPELINE_DIR="src/test/resources/logstash/pipeline"
+def LOGSTASH_LOGS_DIR="target/logs"
+def LOGSTASH_LOGFILE="syslog-test.log"
+
+
+node('linux') {
+      stage('Docker'){
+            checkout scm
+            docker.withRegistry(LOGSTASH_DOCKER_REGISTRY) { 
+                    withEnv(["JAVA_HOME=${tool 'jdk8'}",
+                              'PATH+JAVA=${JAVA_HOME}/bin',
+                              "PATH+MAVEN=${tool 'mvn'}/bin"]) {
+                    def TRAVIS_BUILD_DIR=env.WORKSPACE
+                    sh "mvn clean package --quiet"
+                    sh "mkdir -p ${TRAVIS_BUILD_DIR}/${LOGSTASH_LOGS_DIR}"
+                    sh "touch ${TRAVIS_BUILD_DIR}/${LOGSTASH_LOGS_DIR}/${LOGSTASH_LOGFILE}"
+                    sh "sudo chown 1000 ${TRAVIS_BUILD_DIR}/${LOGSTASH_LOGS_DIR}/${LOGSTASH_LOGFILE}"
+                    sh "sudo chmod g+w ${TRAVIS_BUILD_DIR}/${LOGSTASH_LOGS_DIR}/${LOGSTASH_LOGFILE}"
+                    sh "docker pull ${LOGSTASH_DOCKER_REGISTRY}/${LOGSTASH_DOCKER_IMAGE}:${LOGSTASH_DOCKER_VERSION}"
+                    sh """
+                        docker run -d \
+                      -v ${TRAVIS_BUILD_DIR}/${LOGSTASH_PIPELINE_DIR}:/usr/share/logstash/pipeline \
+                      -v ${TRAVIS_BUILD_DIR}/${LOGSTASH_LOGS_DIR}:/tmp/logs \
+                      -p 127.0.0.1:514:5555 \
+                      -p 127.0.0.1:514:5555/udp \
+                      -e ${LOGSTASH_DOCKER_ENV} \
+                        ${LOGSTASH_DOCKER_REGISTRY}/${LOGSTASH_DOCKER_IMAGE}:${LOGSTASH_DOCKER_VERSION} \
+                     """
+                     sh "mvn verify -DskipIntegrationTests=false"
+                  }
+            }
+      }
+}
+
 buildPlugin()