Remove references to OpenSSL's |wbuf|.

The |wbuf| member is an internal field that disappears in the latest
BoringSSL revision. Also, it doesn't appear to be neccessary: SSL_write
won't report that bytes were written until the record has hit the
transport, so there's no need to be sensitive to an implementation
detail.

(See also cl/100529082.)

Change-Id: I036bb7ebf69649025967a2af467313d7676e62ca
1 file changed