The nuxeo user must be ready for using nuxeoctl

Logging on VM 9.3; the Nuxeo user is not functional: it is necessary to issue export NUXEO_CONF=/etc/nuxeo/nuxeo.conf

At least, the default nuxeo.conf has been removed, avoiding most of the mistakes. Still, the situation is error prone, encouraging users to manually fix what they think being an issue.

The nuxeo service is restrictive and purposed for an automated usage. Thus the need of being able to directly use nuxeoctl with a properly set environment.

=> set up the nuxeo user environment accordingly to the nuxeo service init.