Cleanup, apply only to jruby and add :flaky to tests

gems/aws-sdk-core/spec/aws/plugins/endpoint_discovery_spec.rb

@@ -4,7 +4,7 @@
 
 module Aws
   module Plugins
-    describe EndpointDiscovery do
+    describe EndpointDiscovery, :flaky do
 
       EndpointDiscoveryClient = ApiHelper.sample_service(
         api: {

gems/aws-sdk-core/spec/shared_spec_helper.rb

@@ -10,16 +10,6 @@
 
 require_relative './sigv4_helper'
 
-module RSpec
-  module Core
-    class Example
-      def clear_exception
-        @exception = nil
-      end
-    end
-  end
-end
-
 # Prevent the SDK unit tests from loading actual credentials while under test.
 # By default the SDK attempts to load credentials from:
 #
@@ -62,17 +52,19 @@ def clear_exception
     Thread.report_on_exception = current_value if current_value
   end
 
-  config.around(:each, :flaky) do |example|
-    attempt = 0
-    retries = 3
-    loop do
-      attempt += 1
-      example.run
-      if example.exception && attempt < retries
-        example.example.clear_exception
+  if defined?(JRUBY_VERSION)
+    config.around(:each, :flaky) do |example|
+      attempt = 0
+      retries = 3
+      loop do
+        attempt += 1
+        example.run
+        break if !example.exception || attempt >= retries
+
+        # clear the exception, ensuring it can run from a clean state
+        example.example.instance_variable_set(:@exception, nil)
         redo
       end
-      break
     end
   end
 end