Don't write a new db state entry for a reloaded task proxy.

This results in an IntegrityError for reloaded waiting task proxies
(error is caught and converted to an update, but printed to stdout).
Carry over db_queue to reloaded task proxies.
Record db state at non-reload task init.
Treat restart and reload the same in task proxy init.
Retrieve db ops for all tasks, incl runahead pool.
Split handling of task messages and db ops.
Enforce explicit use of tasks in the runahead pool.
Fixed two runahead tests.
Test #1221
Fixed two runahead tests.

They previously depended on task proxies from the runahead pool not having
entries in the run db.
Merge pull request #1221 from hjoliver/fix-db-update-on-reload

Don't write a new db state entry for a reloaded task proxy.