fixes #6908 - update request tests for latest Chef release

(cherry picked from commit 37c1113f5c1b7c896238f8e0f764241c7bd1cdb7)

Conflicts:
	test/authentication_chef_test.rb
	test/puppet_api_request_test.rb
fixes #7850 - pin mixlib-shellout for Ruby 1.8 compatibility

(cherry picked from commit 56e62d1295ab65e7deca27890ee69e1312ceca0a)

Conflicts:
	bundler.d/test.rb
fixes #7822 - forbid HTTPS requests with no client SSL certificate

(cherry picked from commit 52f0bacf26923826a9b112369d504972369b3cf0)

Conflicts:
	lib/smart_proxy.rb
	lib/smart_proxy_for_testing.rb