Preparing for 4.2.0.beta1 release
Use system /tmp when testing actionpack

https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
added support and enabled parallel execution of the actionpack tests.

However it introduced https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
since one cannot connect to a socket file that's inside a Vagrant synced folder
due to security restrictions, and DRb tries to.

Also rename the temporary files to make it obvious that they're rails-related,
since now they're placed outside the project's directory.

Fixes https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
use self instead of #read_attribute
Demodulize ActiveRecord::MigratorTest
Reset ActiveRecord::Migration.verbose to the value before
No tests are dealing with ActiveRecord::Migration.message_count here anymore
MigrationTest doesn't need to be verbose anymore
Silence another test that runs migrations
Bring original puts back after finishing tests
Reset ActiveRecord::Migration.message_count counter before start testing
[ci skip] Fix example code of ActiveRecord::FixtureSet.context_class
Don't rescue IPAddr::InvalidAddressError

IPAddr::InvalidAddressError does not exist in Ruby 1.9.3
and fails for JRuby in 1.9 mode.

As IPAddr::InvalidAddressError is a subclass of ArgumentError
(via IPAddr::Error) just rescuing ArgumentError is fine.
Merge pull request #16728 from splattael/invalid_address_error

Don't rescue IPAddr::InvalidAddressError
Merge pull request #16739 from y-yagi/patch-6

[ci skip] Fix example code of ActiveRecord::FixtureSet.context_class
Revert "Merge pull request #16254 from zuhao/refactor_activerecord_attribute_decorators_test"

This reverts commit 16fe19831548f108c113094d106663497fc190d5, reversing
changes made to 4c81c8ce533896be28bdc0b055ff30bb9dee1316.

The call to `Model.reset_column_information` was to express the intent of the test.
`reset_column_information` itself can trigger SQL queries because it checks
for a tables existance. Let's move it outside of the block.

/cc @sgrif
[ActiveJob] extract JobBuffer from helper
Merge pull request #16740 from seuros/activejob

[ActiveJob] extract JobBuffer from helper
Don't test PostgreSQL implementation details

Asserting that the message contains "QUERY PLAN" is enough for the adapter's test.
The plan may vary according to number of tuples etc. but that's out of our concern.
Some documentation fixes [ci skip]
Make test:isolated run without bundler for Action Mailer

Action Mailer tests weren't able to run in isolation without the bundle
exec prefix since we were requiring gems before requiring abstract_unit.

We don't need the `gem` call thus and the require_relative since the
test directory should be present in the load path when we run any test.