Merge branch '2.6.next' into 2.6.x

* 2.6.next: (102 commits)
  (puppetlabs#5073) Download plugins even if you're filtering on tags
  Fix puppetlabs#5610: Prevent unnecessary RAL lookups
  Revert "Merge branch 'ticket/2.6.x/5605' of git://github.com/stschulte/puppet into 2.6.next"
  (puppetlabs#6723) Fix withenv environment restoration bug
  (puppetlabs#6689) Remove extraneous include of Puppet::Util in InventoryActiveRecord
  Remove extra trailing whitespace from lib/puppet/resource.rb
  (puppetlabs#5428) More fully "stub" Puppet::Resource::Reference for use with storedconfigs
  (puppetlabs#6707) Fix typo in rest_authconfig.rb
  (puppetlabs#6689) Make inventory_active_record terminus search quickly
  (puppetlabs#5392) Give a better error when realizing a non-existant resource
  (puppetlabs#2645) Adding a less-stubby test to verify the "system" attribute's behavior
  maint: Remove serialization of InventoryFact values
  maint: Rename InventoryHost to InventoryNode
  Fixed puppetlabs#2645 - Added support for creating system users
  maint: Remove spec run noise
  maint:Refactor of mount provider integration tests
  (puppetlabs#6338) Support searching on metadata in InventoryActiveRecord terminus
  (puppetlabs#6338) Implement search for InventoryActiveRecord facts terminus
  (puppetlabs#6338) Add an InventoryActiveRecord terminus for Facts
  Added integration tests for the mount provider
  ...