Support IBM's JVM with default configuration

IBM's JDK used in WAS8 lacks the SUN provider and requires special configuration in order to create a SecureRandom. We want to use the same binary with the same configuration for a mix of servers with different JDK vendors, so we would like the defaults to work with all JDK:s. This solution still allows people to pick the SUN provider using the configuration option. If the option is specified it is always used.