Use current thread resource context instead of system one (#32)

Co-authored-by: Simon Marty <[email protected]>

src/main/java/com/amazonaws/secretsmanager/util/Config.java

@@ -70,7 +70,7 @@ private static Properties loadPropertiesFromConfigFile(String resourceName) {
         InputStream configFile;
 
         try {
-            configFile = ClassLoader.getSystemResourceAsStream(resourceName);
+            configFile = Thread.currentThread().getContextClassLoader().getResourceAsStream(resourceName);
             if(configFile != null) {
                 newConfig.load(configFile);
                 configFile.close();