add foreign keys before modifying them

refs CORE-1069

test plan
 - specs should pass

Change-Id: I0edb8f17e336cbce57e1d44f322b843ca0eb1f30
Reviewed-on: https://gerrit.instructure.com/143595
Reviewed-by: Davis Lynn McClellan <dmcclellan@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>
Tested-by: Jenkins

db/migrate/20130924153118_add_foreign_keys10.rb

@@ -16,7 +16,10 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 
 class AddForeignKeys10 < ActiveRecord::Migration[4.2]
-  tag :postdeploy
+  # this used to be post deploy, but now we need to modify a constraint in a
+  # predeploy so a new database will have the contrainte before it is attempted
+  # to be modified.
+  tag :predeploy
   disable_ddl_transaction!
 
   def self.up

db/migrate/20130924163929_add_foreign_keys11.rb

@@ -16,7 +16,10 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 
 class AddForeignKeys11 < ActiveRecord::Migration[4.2]
-  tag :postdeploy
+  # this used to be post deploy, but now we need to modify a constraint in a
+  # predeploy so a new database will have the contrainte before it is attempted
+  # to be modified.
+  tag :predeploy
   disable_ddl_transaction!
 
   def self.up