lib: Make sure ostream.last_failed_errno is always set when stream_errno is set.
lib: Make sure ostream.last_failed_errno is always set when stream_errno is set.

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