added environment variable to CI docker container for mcserver

.gitlab-ci.yml

@@ -56,7 +56,7 @@ ci_backend:
     - docker:20.10.8-dind
   stage: ci
   script:
-    - docker run --rm --entrypoint="./coverage_backend.sh" $BACKEND_IMAGE > ci_backend.log
+    - docker run --env IS_THIS_A_DOCKER_CONTAINER=Yes --rm --entrypoint="./coverage_backend.sh" $BACKEND_IMAGE > ci_backend.log
   variables:
     DOCKER_DRIVER: overlay2
     DOCKER_TLS_CERTDIR: ""