Lazily instantiate SunJCE.RANDOM

Currently the SunJCE provider instantiates a SecureRandom object during static initialization which is subsequently used for cryptographic operations.

We are exploring loading JCE providers with ServiceLoader for the eventual transition to modules in JDK 9. This can cause potential recursive loading issues if the Sun provider has not been loaded yet (since the providers are loaded in no specific order using ServiceLoader). The fix is to lazily instantiate SunJCE.RANDOM.

This is a proactive fix that will smooth the transition to modules.