make gitea/Jenkinsfile declarative

- fix environment

dockerfiles/services/gitea/Jenkinsfile

@@ -1,6 +1,8 @@
 pipeline {
-    def workdir = 'dockerfiles/services/gitea'
-    def docker_host = 'dkhost:2376'
+    environment {
+        WORKDIR = 'dockerfiles/services/gitea'
+        DOCKER_HOST = 'dkhost:2376'
+    }
 
     agent { label 'docker' }
     options {
@@ -20,17 +22,17 @@ pipeline {
 
         stage('build') {
             steps {
-                dir(workdir) {
-                    sh "DOCKER_HOST=${docker_host} docker-compose -f docker-compose.yml pull"
+                dir(WORKDIR) {
+                    sh "DOCKER_HOST=${DOCKER_HOST} docker-compose -f docker-compose.yml pull"
                 }
             }
         }
 
         stage('deploy') {
             steps {
-                dir(workdir) {
+                dir(WORKDIR) {
                     sh """
-                        export DOCKER_HOST=${docker_host}
+                        export DOCKER_HOST=${DOCKER_HOST}
                         docker stack deploy --with-registry-auth --prune -c docker-compose.yml gitea
                         ../scaleout.sh gitea_app 180
                     """
@@ -40,7 +42,7 @@ pipeline {
 
         stage('smoke tests') {
             steps {
-                dir(workdir) {
+                dir(WORKDIR) {
                     sleep 60
                     sh "curl -If http://dkhost:10080"
                 }