stream-ssl: Enable TLSv1.1 and TLSv1.2.

The Open vSwitch SSL code was inadvertently enabling only TLSv1, not
later versions.  This commit should fix it.

See https://www.openssl.org/docs/ssl/SSL_CTX_new.html
and http://www.postgresql.org/message-id/20131203213049.GA8259@gmail.com
for more information.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Reported-by: Abhinav Singhal <Abhinav.Singhal@spirent.com>
Acked-by: Gurucharan Shetty <gshetty@nicira.com>