In NexusDockerVerveineJRunner, copy the json files created, don't move them

[NicolasAnquetil]

On linux, docker creates model file (json) with root owner (because docker creates a virtual computer that has no idea of the user running docker on the host computer).

This makes it a bit more difficult to handle the file afterward.

1. The known solution to this is copy the file generated to some other location or name (what NexusDockerVerveineJRunner already wants to do) and here the copied file will have the right owner
2. remove the root owned file (needs "forcing it": rm -f) which is possible if it is in a directory owned by the user (with write rights on it). See also Create 'sources' directory explicitly in Pharo #6