Fixes #19789 - fix Layout/SpaceAroundOperators cop

fixes #21694 - Add MTU to subnet

Refs #22164 - use cheaper FactoryBot methods

• Refs #22164 - FactoryBot.build -> FactoryBot.build_stubbed

• Refs #22164 - FactoryBot.create -> FactoryBot.build

in
- test/unit/*
- test/models/shared/taxonomies_base_test.rb
- test/controllers/hosts_controller_test.rb

Fixes #21424 - use factory_bot_rails

Fixes #19825 - Fix Performance/TimesMap cop

refs #16982 - remove User.current deassignment (no such user)

Allows the scope change to be reverted, as User.current is no longer set
to `nil` (there is no 'admin' user).

This was relying on a bug in Ruby on Rails 4.2 where the `unscoped` call
filtered through thread variables into Subnet.subnet_for which calls...

Fixes #16982 - Scope properly when no taxonomies are set

The default scope for hosts and other objects did not restrict
properly by taxonomies. An user without organizations or
locations, could do anything it's permissions allow to.
The list of hosts was unrestricted and showed hosts in...

fixes #18176 - replace clear_association_cache with reload

Reload is still necessary in Rails 5 as interfaces association will be
cached. The BMC test change is necessary to reload smart proxies
associated to the subnet after their features were altered - previously...

fixes #16792 - don't modify AR record attributes in-place

Rails 5 may call #freeze on strings passed in as an attribute during
validation, so attributes must not be edited in-place with gsub! and
similar methods.

fixes #16725 - add plugin extension point for smart proxies