Marconi fixes for precise

Fix a couple of problems found on Ubuntu:
* $MARCONI_DIR/etc/marconi/policy.json doesn't exist; removed the copy to /etc/marconi
* added a seting of nssize in /etc/mongodb.conf for Ubuntu
* restart the correct serice name on Ubuntu

Change-Id: I9bd2ab1aa4fb94ff96559e069e5b62138c358fb5
Merge branch 'marconi-fixes' into dt-test