Ensure QuicTransportStream::Visitor::OnFinRead() is only called once. This fixes a non-deterministic crash in Chromium tests: https://bugs.chromium.org/p/chromium/issues/detail?id=1065854. This also fixes a potential bug in which the stream is never marked as closed. gfe-relnote: n/a (code not used in production) PiperOrigin-RevId: 303787933 Change-Id: I3c4f39e709e27dc5f81ccc78729323da1810fda5