default service's healthcheck need to be fixed in docker-compose.yaml

default service healthcheck is

``` curl --fail http://localhost:8080 ```

This healthcheck has 2 issues, because of which the container always remains in unhealthy state
1. curl is not there in the container
2. localhost:8080 returns 405 always

docker image version: gcr.io/diffgram-open-core/default:1.2.5
diffgram version: 1.2.5