Revert "delete unused method"

This reverts commit a38732c8.

Since the mutation logic was reverted in
07278519, we must bring the reader
method back as well, since the implementation relies on it.

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -232,6 +232,10 @@ def add_transaction_record(record)
         current_transaction.add_record(record)
       end
 
+      def transaction_state
+        current_transaction.state
+      end
+
       # Begins the transaction (and turns off auto-committing).
       def begin_db_transaction()    end