server: Use tdb_check to verify persistent tdbs on startup

server: Use tdb_check to verify persistent tdbs on startup

Depending on --max-persistent-check-errors we allow ctdb
to start with unhealthy persistent databases.

The default is 0 which means to reject a startup with
unhealthy dbs.

The health of the persistent databases is checked after each
recovery. Node monitoring and the "startup" is deferred
until all persistent databases are healthy.

Databases can become healthy automaticly by a completely
HEALTHY node joining the cluster. Or by an administrator
with "ctdb backupdb/restoredb" or "ctdb wipedb".

metze