Disable flaky testBadApkOnly test.

A proper fix for the flakiness has been submitted to more recent
versions of the RollbackTest.

Bug: 139108668
Bug: 139175593

Test: atest StagedRollbackTest

Change-Id: Iad20ac3744b0cf4adf0355150ce957de2a24304c
Merged-In: Iaaa728aa58d894ba546677e8295faba2ebfc5e64

tests/RollbackTest/StagedRollbackTest/src/com/android/tests/rollback/host/StagedRollbackTest.java

@@ -25,6 +25,7 @@ import com.android.tradefed.testtype.junit4.BaseHostJUnit4Test;
 
 import org.junit.After;
 import org.junit.Before;
+import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -63,6 +64,7 @@ public class StagedRollbackTest extends BaseHostJUnit4Test {
      * Tests watchdog triggered staged rollbacks involving only apks.
      */
     @Test
+    @Ignore("b/139175593 flaky test")
     public void testBadApkOnly() throws Exception {
         runPhase("testBadApkOnlyEnableRollback");
         getDevice().reboot();