Pin puppet-collectd

puppet-collectd introduced a change which requires stdlib 4.25:
de0a96e86651 - (2018-03-17 00:12:21 +0100) feat: bump minimum puppetlabs/stdlib version to 4.25.0
c0c5ba9357ea - (2018-03-16 23:54:58 +0100) feat: use Stdlib::Fqdn type for package_keyserver

Let's pin the repo to the change which is already being used in RDO at
https://github.com/redhat-openstack/rdoinfo/blob/master/rdo.yml#L1467

(aka 93c8d0bd32bb5610652f30e785ba6644fc82a8b6 "Merge pull request #751 from bastelfreak/test")

Closes-Bug: #1756890
Change-Id: I197e8036a4f5c790a833d037d03ba6822f5488eb

Puppetfile_extras

@@ -74,9 +74,10 @@ mod 'pacemaker',
   :git => 'https://github.com/openstack/puppet-pacemaker',
   :ref => 'master'
 
+# Note(bandini): Pinned due to LP#1756890
 mod 'collectd',
   :git => 'https://github.com/voxpupuli/puppet-collectd',
-  :ref => 'master'
+  :ref => '93c8d0bd32bb5610652f30e785ba6644fc82a8b6'
 
 # see https://github.com/rdo-packages/puppet-keepalived-distgit/blob/rpm-master/puppet-keepalived.spec
 mod 'keepalived',