EITS: killing the server leaves statistical tables in "marked as crashed" state

If one does the following sequence of operations

• make some action that updates statistical tables (e.g. ANALYZE TABLE ... PERSISTENT FOR ALL).
• kill the server
• start the server again

then any action that attempts read from EITS tables will not be able to open the tables anymore. Opening the table will fail with "table marked as crashed" error.

This task is about making EITS tables more resilient to the scenario.

There are two things to be done:
1. Flush statistical table to disk as soon as we've made any modification (similar to what is done to mysql.proc)
2. Enable auto-repair for statistical tables, like it happens with regular myisam tables.