Add docker login to Jenkinsfile

Jenkinsfile

@@ -32,9 +32,14 @@ pipeline {
             when {
                 not { environment name: 'GIT_TAG', value: '' }
             }
+            environment {
+                DOCKERHUB = credentials('dockerhub')
+            }
             steps {
+                sh 'docker login -u $DOCKERHUB_USR -p $DOCKERHUB_PSW'
                 sh 'make tag'
                 sh 'make push'
+                sh 'docker logout'
             }
         }
     }