databases/couchdb2: detach stdout from daemon invocation

When CouchDB is started whithout a parent tty, for example, via ssh,
the daemon invocation retains a connection to stdout, thus blocking
disconnection of the ssh command.

The Erlang VM provides a -detach flag for avoiding this situation.
Add additional notes on debugging to the config file to aid users.

PR: 234100
Reported by: Reshad Patuck <reshadpatuck1@gmail.com>
Reviewed by: Reshad Patuck <reshadpatuck1@gmail.com>
Approved by: jrm (mentor)