[test] disable few tests on JRuby < 9.1

Author: kares

src/test/ruby/dsa/test_dsa.rb

@@ -183,7 +183,7 @@ def test_PUBKEY
     assert_equal asn1.value[0].value[1].value[2].value, OpenSSL::ASN1.decode(dup_der).value[0].value[1].value[2].value
 
     assert_equal pem, dup_public(dsa512).export
-  end
+  end if !defined?(JRUBY_VERSION) || JRUBY_VERSION > '9.1' # set_pqg only since Ruby 2.3
 
   def test_read_DSAPublicKey_pem
     # NOTE: where is the standard? PKey::DSA.new can read only PEM

src/test/ruby/rsa/test_rsa.rb

@@ -177,7 +177,7 @@ def test_RSAPublicKey
 
     expected = "b48c0b2bbd35b906c5af4e46ed7355e4aaeadc99"
     assert_equal expected, OpenSSL::Digest::SHA1.hexdigest(key.to_der)
-  end
+  end if !defined?(JRUBY_VERSION) || JRUBY_VERSION > '9.1' # set_key only since Ruby 2.3
 
   private