login to correct registry

azure-pipelines.yml

@@ -2,7 +2,7 @@ pool:
   vmImage: 'Ubuntu 16.04'
 
 steps:
-- script: docker login -u "$(ACR_USER)" -p "$(ACR_PASSWORD)"
+- script: docker login "$(ACR_REGISTRY)" -u "$(ACR_USER)" -p "$(ACR_PASSWORD)"
   displayName: Docker Login
 - script: docker build . -t "$(DOCKER_IMAGE_NAME)"
   displayName: Docker Build