This commit improves TLS messages framing by avoiding an extra call to
SSL_write_ex(). Before that we would use an extra SSL_write_ex() call
to pass DNS message length to OpenSSL. That could create an extra TLS
frame, increasing number of bytes sent due to frame header and
padding.
This commit fixes that by making the code pass both DNS message length
and data at once, just like old TLS code did.
It should improve compatibility with some buggy clients that expect
both DNS message length and data to be in one TLS frame.
Older TLS DNS code worked like this, too.
20d5a805e2