(maint) install puppet-agent package

install_puppet_on was installing the Debian repo puppet pacakges which
have Puppet 5.4.0, not puppet-agent 5.5.x

Author: austb

Diff for: spec/spec_helper_acceptance.rb

@@ -83,7 +83,9 @@ def build_url(platform)
   end
 end
 
-install_puppet_on(hosts) unless ENV['BEAKER_provision'] == 'no'
+opts = {puppet_agent_version: 'latest'}
+opts[:puppet_collection] = use_puppet5? ? 'puppet5' : 'puppet6'
+install_puppet_agent_on(hosts, opts) unless ENV['BEAKER_provision'] == 'no'
 install_ca_certs unless ENV['PUPPET_INSTALL_TYPE'] =~ %r{pe}i
 install_module_on(hosts)
 install_module_dependencies_on(hosts)