Harden default TLS configuration (RIPD-1332, RIPD-1333, RIPD-1334):

The existing configuration includes 512 and 1024 bit DH
parameters and supports ciphers such as RC4 and 3DES and
hash algorithms like SHA-1 which are no longer considered
secure.

Going forward, use only 2048-bit DH parameters and define
a new default set of modern ciphers to use:

    HIGH:!aNULL:!MD5:!DSS:!SHA1:!3DES:!RC4:!EXPORT:!DSS

Additionally, allow administrators who wish to have different
settings to configure custom global and per-port ciphers suites
in the configuration file using the `ssl_ciphers` directive.

src/test/overlay/short_read_test.cpp

@@ -555,7 +555,7 @@ public:
                 beast::Thread::setCurrentThreadName("io_service");
                 this->io_service_.run();
             }))
-        , context_(make_SSLContext())
+        , context_(make_SSLContext(""))
     {
     }