Disable reports by default

The default value for this goes all the way back to when it was
introduced in 566bf78. I'd argue it a
bad default, because it just writes files without any clean up process
in place. That only causes hard disks to fill up.

Having reports should be an opt in feature, where they make a careful
choice. PuppetDB is an obvious recommended option but not one that can
be relied on by default.

lib/puppet/defaults.rb

@@ -1477,7 +1477,7 @@ def self.initialize_default_settings!(settings)
       :mode => "0750",
       :desc => "The directory in which serialized data is stored, usually in a subdirectory."},
     :reports => {
-      :default    => "store",
+      :default    => "none",
       :desc       => "The list of report handlers to use. When using multiple report handlers,
         their names should be comma-separated, with whitespace allowed. (For example,
         `reports = http, store`.)