Use correct option name for the database connection

This fixes a problem introduced with 5ce199c3
Remove auto_assign_floating_ip option again

This does not make sense when using quantum
Revert "The database setup needs only be executed on the control node (bnc#780406)"

This reverts commit 985b9ce5a3fc3bb7daa120d800bba357aa3e3c4a.
nova-compute doesn't need database