The CWM might prevent a stream from being writeable. We should not report
a stream as writeable if there is no credit.
Fixes#27312
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/27319)