dbox file fixing: If I/O error happens during read, don't finish the fix.
dbox file fixing: If I/O error happens during read, don't finish the fix.

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot