(MODULES-11112) Add parameter puppet_agent::proxy

This is to be able to configure yum-repo with proxy, needed for
example for clients in dmz:s that need to use proxy to reach the repo
provided by puppetserver.

Author: chrekh

manifests/init.pp

@@ -119,6 +119,7 @@
   $alternate_pe_source     = undef,
   $install_dir             = undef,
   $disable_proxy           = false,
+  $proxy                   = undef,
   $install_options         = [],
   $skip_if_unavailable     = 'absent',
   $msi_move_locked_files   = false,

manifests/osfamily/redhat.pp

@@ -145,7 +145,7 @@
     if $::puppet_agent::manage_repo == true {
       $_proxy = $::puppet_agent::disable_proxy ? {
         true    => '_none_',
-        default => undef,
+        default => $::puppet_agent::proxy,
       }
       yumrepo { 'pc_repo':
         baseurl             => $source,