SSLv3 guard broken in ruby 1.8.7 and 1.9.3

Net::HTTP in ruby 1.8.7 injects params to own @ssl_context instead of
calling SSLContext#set_params.

Also there's a silly bug in custom set_params that does not set
SSLContext parameters properly. I confirmed the fix with
'openssl s_server -ssl3' command, all of 1.8.7, 1.9.3, 2.0 and 2.1.