Don't expect conneciton_pool.current_pool to exist

current_pool was an old switchman special that isn't needed on rails 6.1+

fixes CANVAS-HWDH

Change-Id: I98c60154b5a572669adeaada5e8cfe8dc1347033
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/287731

Reviewed-by: Aaron Ogata <aogata@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Jacob Burroughs <jburroughs@instructure.com>
Product-Review: Jacob Burroughs <jburroughs@instructure.com>

app/models/auditors/active_record/partitioner.rb

@@ -45,7 +45,13 @@ module Auditors::ActiveRecord
             end
             log "*" * 80
           end
-          ActiveRecord::Base.connection_pool.current_pool.disconnect! unless Rails.env.test?
+          unless Rails.env.test?
+            if CANVAS_RAILS6_0
+              ActiveRecord::Base.connection_pool.current_pool.disconnect!
+            else
+              ActiveRecord::Base.connection_pool.disconnect!
+            end
+          end
         end
       end
     end

app/models/messages/partitioner.rb

@@ -22,7 +22,13 @@ module Messages
 
           log "Done. Bye!"
           log "*" * 80
-          ActiveRecord::Base.connection_pool.current_pool.disconnect! unless Rails.env.test?
+          unless Rails.env.test?
+            if CANVAS_RAILS6_0
+              ActiveRecord::Base.connection_pool.current_pool.disconnect!
+            else
+              ActiveRecord::Base.connection_pool.disconnect!
+            end
+          end
         end
       end
     end

app/models/quizzes/quiz_submission_event_partitioner.rb

@@ -38,7 +38,13 @@ class Quizzes::QuizSubmissionEventPartitioner
 
         log "Done. Bye!"
         log "*" * 80
-        ActiveRecord::Base.connection_pool.current_pool.disconnect! unless in_migration || Rails.env.test?
+        unless in_migration || Rails.env.test?
+          if CANVAS_RAILS6_0
+            ActiveRecord::Base.connection_pool.current_pool.disconnect!
+          else
+            ActiveRecord::Base.connection_pool.disconnect!
+          end
+        end
       end
     end
   end

app/models/simply_versioned/partitioner.rb

@@ -36,7 +36,13 @@ class SimplyVersioned::Partitioner
 
         log "Done. Bye!"
         log "*" * 80
-        ActiveRecord::Base.connection_pool.current_pool.disconnect! unless Rails.env.test?
+        unless Rails.env.test?
+          if CANVAS_RAILS6_0
+            ActiveRecord::Base.connection_pool.current_pool.disconnect!
+          else
+            ActiveRecord::Base.connection_pool.disconnect!
+          end
+        end
       end
     end
   end

app/models/stream_item.rb

@@ -399,7 +399,13 @@ class StreamItem < ActiveRecord::Base
       Shard.current.database_server.unguard do
         StreamItem.vacuum
         StreamItemInstance.vacuum
-        ActiveRecord::Base.connection_pool.current_pool.disconnect! unless Rails.env.test?
+        unless Rails.env.test?
+          if CANVAS_RAILS6_0
+            ActiveRecord::Base.connection_pool.current_pool.disconnect!
+          else
+            ActiveRecord::Base.connection_pool.disconnect!
+          end
+        end
       end
     end