Fix 12 Boring tests involving NULL-SHA ciphersuites

The Boring runner attempts to enable the NULL-SHA ciphersuite using the
cipherstring "DEFAULT:NULL-SHA". However in OpenSSL DEFAULT permanently
switches off NULL ciphersuites, so we fix this up to be "ALL:NULL-SHA"
instead. We can't change the runner so we have to change the shim to
detect this.

(Merged from https://github.com/openssl/openssl/pull/2933

)
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Emilia Käsper <emilia@openssl.org>