Use CertificateFactory.getInstance rather than reflection

Perhaps this method was not accessible before, but it is now and
this change eliminates one of the module warnings we have been
seeing in #161.

Author: headius

src/main/java/org/jruby/ext/openssl/SecurityHelper.java

@@ -266,10 +266,7 @@ static CertificateFactory getCertificateFactory(final String type, final Provide
         throws CertificateException {
         final CertificateFactorySpi spi = (CertificateFactorySpi) getImplEngine("CertificateFactory", type);
         if ( spi == null ) throw new CertificateException(type + " not found");
-        return newInstance(CertificateFactory.class,
-                new Class[]{ CertificateFactorySpi.class, Provider.class, String.class },
-                new Object[]{ spi, provider, type }
-        );
+        return CertificateFactory.getInstance(type, provider);
     }
 
     /**