Call Db_Adapter_Interface::startSetup() & endSetup() for table fixtures

Given a table fixtures like this:

tables:
  customer/customer_group:
    - customer_group_id: 0
      customer_group_code: NOT LOGGED IN
      tax_class_id: 3
    - customer_group_id: 1
      customer_group_code: General
      tax_class_id: 3

The primary key 0 will be affected by the mysql auto increment setting,
So in this example the customer_group_id for the group NOT LOGGED IN
would be the next auto_increment value for that column table.
Calling Varien_Db_Adapter_Pdo_Mysql::startSetup() calls
"SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO'" which
fixes this behaviour.