AU: Disallow Anonymous Diffie Hellman ciphers

BUG=9062
TEST=tested that things didn't break on device/unittest

Review URL: http://codereview.chromium.org/5406001

Change-Id: Ic5832cbef0fbfc3dcf61f7d24b468e77f61d9870
diff --git a/libcurl_http_fetcher.cc b/libcurl_http_fetcher.cc
index 2502b6d..cdc7523 100644
--- a/libcurl_http_fetcher.cc
+++ b/libcurl_http_fetcher.cc
@@ -140,7 +140,8 @@
                               CURLOPT_REDIR_PROTOCOLS,
                               CURLPROTO_HTTPS),
              CURLE_OK);
-    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_CIPHER_LIST, "HIGH"),
+    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_CIPHER_LIST,
+                              "HIGH:!ADH"),
              CURLE_OK);
   }