Fix test_client_hello with no-tls1_2_method

The extensions not sent when TLS 1.2 is not used caused the message
length to be 109, which is less than the 127 threshold needed
to activate the F5 workaround.  Add another 20 bytes of dummy ALPN
data do push it over the threshold.

Also, fix the definition of the (unused) local macro indicating
the threshold.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4346)