Currently qdr::listener_port is set to a string by default and triggers
the following warning.
validate_legacy(validate_re) expects an Integer value, got String at
["/etc/puppetlabs/code/modules/qdr/manifests/init.pp", 198]:
This change fixes type validation logic about the parameter to get rid
of the warning.
Change-Id: I78203816bd91c8efe0673045fdc6956c83044053