updater_sample: fix UpdateConfig

- fix UpdateConfig
- fix smaple.json
- fix FileDownloaderTest

Test: manually
Change-Id: I09d272f77c89a02f54a24cf753fdfda4ce243927
Signed-off-by: Zhomart Mukhamejanov <zhomart@google.com>
diff --git a/updater_sample/tests/src/com/example/android/systemupdatersample/util/FileDownloaderTest.java b/updater_sample/tests/src/com/example/android/systemupdatersample/util/FileDownloaderTest.java
index 009610e..a136ff0 100644
--- a/updater_sample/tests/src/com/example/android/systemupdatersample/util/FileDownloaderTest.java
+++ b/updater_sample/tests/src/com/example/android/systemupdatersample/util/FileDownloaderTest.java
@@ -16,7 +16,7 @@
 
 package com.example.android.systemupdatersample.util;
 
-import static junit.framework.Assert.assertEquals;
+import static org.junit.Assert.assertEquals;
 
 import android.content.Context;
 import android.support.test.InstrumentationRegistry;