Merge branch 'fix/pipeline-id-metrics-migration' into 'master'

Fix migration missing ignored transaction method

Adds missing `disable_ddl_transaction!` to migration

See merge request !7569

db/migrate/20161020083353_add_pipeline_id_to_merge_request_metrics.rb

@@ -4,6 +4,8 @@
 class AddPipelineIdToMergeRequestMetrics < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
+  disable_ddl_transaction!
+
   # Set this constant to true if this migration requires downtime.
   DOWNTIME = true