Now that the iproto protocol has sc_schema_id, fix net.box as well as all other drivers to perform "soft" schema reload. I call this strategy "soft", since there are many ways to deal with schema changes, and this is only one of them.

So what net.box should do by default:

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