[server/session] add missing rollback when freeing a db connection When we let go of a cnxset and give it back to the pool, we need to make sure it's not in the middle of a transaction. We got bitten by a migration where the connection used by admin's repo.connect was not rolled back before attempting the migration, causing a deadlock because it had a lock on a table. This could potentially also be an issue for e.g. hooks or looping tasks that didn't explicitly rollback before calling free_cnxset or moving out of a ensure_cnx_set block.

import ConfigParser
try:
    undo_actions = config.cfgfile_parser.get('MAIN', 'undo-support', False)
except ConfigParser.NoOptionError:
    pass # this conf. file was probably already migrated
else:
    config.global_set_option('undo-enabled', bool(undo_actions))