public static String getTrustStoreLocation() {
        String trustStoreLoc = System.getProperty("javax.net.ssl.trustStore");
        return trustStoreLoc == null ? getKeyStoreLocation() : trustStoreLoc;
    }
Return JVM param set truststore location, or keystore location if not
set. if keystore not set either, returns default

@return truststore location as string
src/test/java/spark/util/SparkTestUtil.java