Fixes #12241 - Correct counter_cache deadlock fix

Previous fix had a bug - in `:after_commit` `self.changes` is empty, and the
changes are in `self.previous_changes`. Also this only needs to run on
update.
This commit adds tests to make sure cached_counters continue to work...

fixes #11965 - hostgroup with config group - clone should not run validations more than once

Fixes #11924 - Substitute .scoped by .where(nil) to force return relation

On Rails 4 .scoped is deprecated. Calling .all on the model returns the
equivalent ActiveRecord relation object on Rails 4, but on Rails 3 it
returns an Array right away.

A proper replacement we can use is where(nil) - it's ugly but it returns...

fixes #9981 - making sure lookup_keys with errors get displayed if they're broken

fixes #11124 - Interface compute attributes not merged from API request over compute profile

fixes #12109 - removing owner_id presence validation

in rails 4, owner is not populated when creating a join model
(user.roles << role created a UserRole on the background)
in rails 3, this is not a problem, in rails 4, the presence validation
fails because no owner_id exists nor does an owner exist. at that...

Fixes #12089 - fix using unwrapped parameters in config templates API controller

Fixes #11921 - load dynamic features during runtime

Refs #12155 - Use Proc instead of lambda on mailer for Rails 4

Problem:
On Rails 3, using a lambda with no arguments works fine in an
ActionMailer default. However on Rails 4, the lambda will whine because
there is no handling of arguments and ActionMailer is trying to pass a...

fixes #12207 - objects with ancestors should not call ancestors if cached

up until now, ancestry objects always called their ancestors when
linking to the object because to_param called get_title instead of title
(which can be cached)
this caused a LOT of pointless queries, slowed down Hosts#index alot