Fix Dockerfile entrypoint (#4976)
Fix Dockerfile entrypoint (#4976)

* Fix Dockerfile entrypoint

Fix WORKDIR and use symlink to setup working defaults for config flags.

Signed-off-by: Ben Kochie <9bbf917dc63fbaa40c67921332d26cf16a50db75@gmail.com>

* Collapse Dockrefile RUNs

Signed-off-by: Ben Kochie <9bbf917dc63fbaa40c67921332d26cf16a50db75@gmail.com>

keegancsmith/prometheus,kangwoo/prometheus,keegancsmith/prometheus,alileza/prometheus,prometheus/prometheus,keegancsmith/prometheus,prometheus/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,alileza/prometheus,kangwoo/prometheus,Gouthamve/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,alileza/prometheus