fix time race condition in spec

Change-Id: I8fc83f66f3e6c82c619cc077a50a811ab70c2068
Reviewed-on: https://gerrit.instructure.com/9729
Reviewed-by: Zach Wily <zach@instructure.com>
Tested-by: Brian Palmer <brianp@instructure.com>

spec/models/submission_spec.rb

@@ -119,7 +119,7 @@ describe Submission do
       Time.stubs(:now).returns(new_time)
       @entry2 = @topic.discussion_entries.create(:message => "second entry", :user => @user)
       @submission.reload
-      @submission.submitted_at.to_s(:db).should eql @submission.created_at.to_s(:db)
+      (@submission.submitted_at.to_i - @submission.created_at.to_i).abs.should < 1.minute
     end
   end