Add "daemon" flag to marconi script

This patch adds daemon flag to marconi script. This change was
needed to run the latest build of marconi-server in background.
Since mongodb can not be used with marconi until gate is updated
to Ubuntu 14.04, we are changing our backend to sqlite.

Change-Id: I1a4148bd545818d5e943257be2f6e752ce43f793
Merge "Add "daemon" flag to marconi script"