Fix migrations not specifying DOWNTIME

Signed-off-by: Rémy Coutable <remy@rymai.me>

db/migrate/20160615142710_add_index_on_requested_at_to_members.rb

@@ -5,7 +5,11 @@ class AddIndexOnRequestedAtToMembers < ActiveRecord::Migration
   disable_ddl_transaction!
-  def change
+  def up
     add_concurrent_index :members, :requested_at
   end
+
+  def down
+    remove_index :members, :requested_at if index_exists? :members, :requested_at
+  end
 end

db/migrate/20160620115026_add_index_on_runners_locked.rb

@@ -8,7 +8,11 @@ class AddIndexOnRunnersLocked < ActiveRecord::Migration
   disable_ddl_transaction!
-  def change
+  def up
     add_concurrent_index :ci_runners, :locked
   end
+
+  def down
+    remove_index :ci_runners, :locked if index_exists? :ci_runners, :locked
+  end
 end

db/migrate/20160715134306_add_index_for_pipeline_user_id.rb

 class AddIndexForPipelineUserId < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
+  DOWNTIME = false
+
   disable_ddl_transaction!
-  def change
+  def up
     add_concurrent_index :ci_commits, :user_id
   end
+
+  def down
+    remove_index :ci_commits, :user_id if index_exists? :ci_commits, :user_id
+  end
 end