Fix use-after-free in BIO_C_SET_SSL callback
Fix use-after-free in BIO_C_SET_SSL callback

Since the BIO_SSL structure was renewed by `ssl_free(b)/ssl_new(b)`,
the `bs` pointer needs to be updated before assigning to `bs->ssl`.

Thanks to @suishixingkong for reporting the issue and providing a fix.

Closes #10539

Reviewed-by: Tomas Mraz <973cc78d8b4cb00714230ba9be0225e917ab4ac6@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/11746)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl