Fix autoload race in Aws::EC2::*

[jkeiser]

by accessing the resources we need in driver initialize.

Tests for this are hard to write because they have to run separately. Here is the test I ran:

require "kitchen/driver/ec2"

ec2 = Kitchen::Driver::Ec2.new({})
threads = (1..1000).map do
  Thread.new do
    begin
      ec2.ec2.resource
    rescue
      STDERR.puts "Noooo #{$!}"
    end
  end
end
threads.each { |t| t.join }

If I run this before my patch, it prints out "Nooooo uninitialized constant Aws::EC2::Resource" multiple times. After the patch, it doesn't print it out.

[ksubrama]

👍

[mwrock]

👍