docker: Run parallel by default

[why]
When nothing is specified there is only one patcher running instead of
number-of-threads patchers. But we want the speedup as default.

[how]
Use `-j0`, although it has a small bug. We could also use `-j100%` but
then the output might confuse people even more?

Reported-by: nobk <nobk@noreply.github.com>
Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

bin/scripts/docker-entrypoint.sh

@@ -21,7 +21,7 @@ while [ "$#" -gt 0 ]; do
 done
 
 if [ -z "$PN" ]; then
-	PN=1
+	PN=0
 fi
 
 printf "Running with options:\n%s\nParallelism %s\n" "$args" "$PN"