[server/session] remove json dumps around call_service This backouts changeset b151beea9cb6. With call_service being in-process and synchronous, there's no RPC use case.

#! /bin/sh -e
 
case "$1" in
    purge)
	rm -rf /etc/cubicweb.d/
	rm -rf /var/log/cubicweb/
	rm -rf /var/lib/cubicweb/
    ;;
esac
 
#DEBHELPER#
 
exit 0