Fix for negative return value from `SSL_CTX_sess_accept()`
Fixes #13183
From the original issue report, before this commit, on master and on
1.1.1, the issue can be detected with the following steps:
- Start with a default SSL_CTX, initiate a TLS 1.3 connection with SNI,
"Accept" count of default context gets incremented
- After servername lookup, "Accept" count of default context gets
decremented and that of SNI context is incremented
- Server sends a "Hello Retry Request"
- Client sends the second "Client Hello", now again "Accept" count of
default context is decremented. Hence giving a negative value.
This commit fixes it by adding a check on `s->hello_retry_request` in
addition to `SSL_IS_FIRST_HANDSHAKE(s)`, to ensure the counter is moved
only on the first ClientHello.
CLA: trivial
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/13297)