crypto/tls: change advertised ciphersuite order.

crypto/tls: change advertised ciphersuite order.

TLS clients send ciphersuites in preference order (most prefereable
first). This change alters the order so that ECDHE comes before plain
RSA, and RC4 comes before AES (because of the Lucky13 attack).

This is unlikely to have much effect: as a server, the code uses the
client's ciphersuite order by default and, as a client, the non-Go
server probably imposes its order.

R=golang-dev, r, raggi, jsing
CC=golang-dev
https://golang.org/cl/10372045