Annotating a job test as flaky

The test can be flaky at times and block presubmit.

Test: atest FrameworksServicesTests:BackgroundRestrictionsTest

Fixes: 265169500
Change-Id: I42cba7b35f899777acd4a0149ce66f2c1710dfa7

services/tests/servicestests/src/com/android/server/job/BackgroundRestrictionsTest.java

@@ -165,6 +165,7 @@ public class BackgroundRestrictionsTest {
                 awaitJobStart(DEFAULT_WAIT_TIMEOUT));
     }
 
+    @FlakyTest
     @Test
     public void testFeatureFlag() throws Exception {
         Settings.Global.putInt(mContext.getContentResolver(),