For mongo service, change the "sleep 3" instruction into "mongostat -n 1".
The instruction meant to wait for the server startup procedure.
Mongostat should print up when such procedure are completed meanwhile "sleep"
is infrastucture dependent
For opensilex service, reply the "chown" command at the entry point time.
The mounted volume remaind owned by root:root otherwise and the config file
could not be generated. (Not reproduced)