soft automatic schema reload

[kostja]

Now that the iproto protocol has sc_schema_id, fix the driver to perform "soft" schema reload.

• load the current schema automatically when connection is established
• include sc_schema_id in queries
• if the response is ER_SCHEMA_CHANGED, reload the schema and re-issue the query.

https://github.com/tarantool/tarantool/issues/1183