https://github.com/Katello/puppet-qpid/commit/9c46759d62fd099491327e679fc4a1b90aaf9f8c added this parameter (included in katello-installer 3.4). This is not exposed as a top level parameter but can be set through custom-hiera.yaml.
Setting qpid::max_connections in custom-hiera.yaml should work in the 6.3 beta
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.