remove transaction around saving scores

Removes a database transaction in the grade calculator that is scoped
around too much work.  The transaction was originally added before
postgres's upsert capability for two statements. Over time, more and
more work was added leading to deadlocks in production.

test plan:
 - spec pass

Change-Id: Ia95035be6934b148f8d836bf4419f978a0b45918
Reviewed-on: https://gerrit.instructure.com/212873
Reviewed-by: Spencer Olson <solson@instructure.com>
Reviewed-by: Derek Bender <djbender@instructure.com>
Tested-by: Jenkins
QA-Review: Keith Garner <kgarner@instructure.com>
Product-Review: Keith Garner <kgarner@instructure.com>

lib/grade_calculator.rb

@@ -427,19 +427,13 @@ class GradeCalculator
 
     @course.touch
 
-    save_scores_in_transaction
-  end
-
-  def save_scores_in_transaction
-    Score.transaction do
-      @course.shard.activate do
-        save_course_and_grading_period_scores
-        save_course_and_grading_period_metadata
-        score_rows = group_score_rows
-        if @grading_period.nil? && score_rows.any?
-          dropped_rows = group_dropped_rows
-          save_assignment_group_scores(score_rows.join(','), dropped_rows.join(','))
-        end
+    @course.shard.activate do
+      save_course_and_grading_period_scores
+      save_course_and_grading_period_metadata
+      score_rows = group_score_rows
+      if @grading_period.nil? && score_rows.any?
+        dropped_rows = group_dropped_rows
+        save_assignment_group_scores(score_rows.join(','), dropped_rows.join(','))
       end
     end
   end