Fix broken test by increasing Thread#join timeout

The timeout was added in ag/19606284 but it seems 1ms wasn't enough for
the work to complete so the test as almost 100% flaky.

Test: atest UserBackupManagerServiceTest
Fixes: 276437270

Change-Id: Ie8ff85d8fc52ae9e9d80778131afc0bf8a8eedd6
diff --git a/services/tests/mockingservicestests/src/com/android/server/backup/UserBackupManagerServiceTest.java b/services/tests/mockingservicestests/src/com/android/server/backup/UserBackupManagerServiceTest.java
index b9bfcb0..bed1e97 100644
--- a/services/tests/mockingservicestests/src/com/android/server/backup/UserBackupManagerServiceTest.java
+++ b/services/tests/mockingservicestests/src/com/android/server/backup/UserBackupManagerServiceTest.java
@@ -84,7 +84,7 @@
     private static final String TEST_PACKAGE = "package1";
     private static final String[] TEST_PACKAGES = new String[] { TEST_PACKAGE };
     private static final String TEST_TRANSPORT = "transport";
-    private static final int WORKER_THREAD_TIMEOUT_MILLISECONDS = 1;
+    private static final int WORKER_THREAD_TIMEOUT_MILLISECONDS = 100;
     @UserIdInt private static final int USER_ID = 0;
 
     @Mock IBackupManagerMonitor mBackupManagerMonitor;