Don't use the MYSQL* returned from mysql_real_connect to overwrite the already initalised mysql variable


client/mysqlslap.c:
  Only use the MYSQL* returned from mysql_reqal_connect as an indicator wether the connect was successfull or not.
  As the manual says about the return value from mysql_real_connect: "A MYSQL* connection handle if the connection
  was successful, NULL if the connection was unsuccessful. For a successful connection, the 
  return value is the same as the value of the first parameter."