Container start command at Dockerfile always use default instances.yml

[vrogach2020]

If I want to pass a different from instancesFile ctor parameter this will not work.
We need to patch Dockerfile and add cfg option to cartridge command. For example:

CMD cartridge build && cartridge start --run-dir=$TARANTOOL_RUNDIR --data-dir=$TARANTOOL_DATADIR --cfg=$INSTANCES_FILE