SSL_set_bio has some rather complex ownership story because whether rbio/wbio
are both owning depends on whether they are equal. Moreover, whether
SSL_set_bio(ssl, rbio, wbio) frees ssl->rbio depends on whether rbio is the
existing rbio or not. The current logic doesn't even get it right; see tests.
Simplify this. First, rbio and wbio are always owning. All the weird ownership
cases which we're stuck with for compatibility will live in SSL_set_bio. It
will internally BIO_up_ref if necessary and appropriately no-op the left or
right side as needed. It will then call more well-behaved ssl_set_rbio or
ssl_set_wbio functions as necessary.
Change-Id: I6b4b34e23ed01561a8c0aead8bb905363ee413bb
Reviewed-on: https://boringssl-review.googlesource.com/8240
Reviewed-by: Adam Langley <agl@google.com>
f715c42322