[TUBEMQ-138] Optimize core module test case code

[viviel]

1. Optimize the use of assertions
2. Fix possible null pointer exception

SSLEngine sslEngine = null;
try {
    // create engine
    sslEngine = TSSLEngineUtil.createSSLEngine(keyStorePath, trustStorePath,
    keyStorePassword, trustStorePassword, true, false);
} catch (Throwable e) {
    e.printStackTrace();
}
// If the above code is a field, it may cause the object sslEngine is null
boolean needClientAuth = sslEngine.getNeedClientAuth();

[gosonzhang]

+1