Logins possible during recovery, risk of corrupting repository

When the stone crashes, on restart it performs recovery using the transaction
logs to recover all work done up to the point of the crash.

It was possible for user sessions to log in during this recovery, and commit
changes. This corrupts the repository, making it unusable.

Workaround:

Ensure that no sessions log in until the recovery is complete; pay particular
attention to an automated jobs.

Note bug #41469, waitstone may return ready during stone recovery; do not
use waitstone as a test that the recovery is complete. startstone will
not return to the prompt until recovery is complete and is a safe test.