Docker is very strict with it's json format and doesnt
seem to allow any surprise new lines or extra commas
after the last option before the closing }.
Since this is a dynamically constructed file, we dont know
what the last option will be. By putting the commas at the
start of the line and removing all newspace, we remove
the problem, at the expense of a less readable jinja
template.
Patrick Marchand
Ludovic Poujol
