If you don't have the cloudera-manager-server-db-2 package, how do you have the db.mgmt.properties file?
Did you remove it at some point?
In any case, a couple things:
You don't need Activity Monitor role unless you are using MapReduce1. You can not use that role.
It appears you have not entered hostname and port in the Database Setup
If you do have a /etc/cloudera-scm-server/db.mgmt.properties, please remove it from that directory. It is possible that its presence is causing problems for the connection test as you should not have db.mgmt.properties if you are not using the embedded database. All database configurations except for Cloudera Manager's are stored in Cloudera Manager's database, not in flat files.