MINOR: ssl: don't use boringssl's cipher_list

MINOR: ssl: don't use boringssl's cipher_list

Google's boringssl has a different cipher_list, we cannot use it as
in OpenSSL. This is due to the "Equal preference cipher groups" feature:

https://boringssl.googlesource.com/boringssl/+/858a88daf27975f67d9f63e18f95645be2886bfb^!/

also see:
https://www.imperialviolet.org/2014/02/27/tlssymmetriccrypto.html

cipher_list is used in haproxy since commit f46cd6e4ec3a ("MEDIUM: ssl:
Add the option to use standardized DH parameters >= 1024 bits") to
check if DHE ciphers are used.

So, if boringssl is used, the patch just assumes that there is some
DHE cipher enabled. This will lead to false positives, but thats better
than compiler warnings and crashes.

This may be replaced one day by properly implementing the the new style
cipher_list, in the meantime this workaround allows to build and use
boringssl.

Signed-off-by: Lukas Tribus <luky-37@hotmail.com>