Upgraded mongo on my devstack direct to 3.4 via: https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/

Kept existing /etc/mongod.conf

• Needed to update due to error "BadValue: Can't specify both --journal and --nojournal options." just commented out the --journal line.

• sudo service mongod start - different starting mechanism, needs manual start at this point

Ran mongo, connects. db.version() is correct

paver test

Worked with no changes or errors