ci(azure-pipelines): use Dockerfile in root dir

azure-pipelines.yaml

@@ -30,6 +30,7 @@ jobs:
           pwd
           ls -a .
           ls -a $(Build.Repository.LocalPath)
+          cp docker/backend/Dockerfile .
           docker build \
           --build-arg HTTPS_PROXY=http://proxy.frankfurt-airport.de:8080 \
           --build-arg HTTP_PROXY=http://proxy.frankfurt-airport.de:8080 \
@@ -37,7 +38,7 @@ jobs:
           --build-arg FROM_IMG=devfra.azurecr.io/de.fraport.build/haskell \
           --build-arg MOUNT_DIR=$(Build.Repository.LocalPath) \
           --build-arg PROJECT_DIR=/fradrive \
-          --file docker/backend/Dockerfile
+          .
     - task: Docker@2
       name: dockerLoginDevFra
       displayName: Docker Login to devfra