Provide dynamic code-generated certificates for HTTP tests to avoid expiry

As documented, the test certificates/keys used in the TestInvokeHttp and TestInvokeHttpSSL tests expired in 2014. With the constant removal of non-certificate based cipher suites from client libraries, the lack of valid certificates meant that the Jetty server could not offer any compatible cipher suites, and the tests failed. I manually generated and loaded new certificates but they expire after 1 year. Adding code to dynamically generate and load these certificates into the keystore and truststore would remove this inconsistent blocker.