Do not allow multiple commits of the same rollback.

A small improvement to UX, to avoid seeing FAIL rollbacks,
when the rollback has been a SUCCESS on a first try.

Bug: 220204580
Test: manual
Change-Id: I12957a7cdf2499d7ff6f9ce4e0dcc0e568927e6d

tests/RollbackTest/SampleRollbackApp/src/com/android/sample/rollbackapp/MainActivity.java

@@ -75,6 +75,7 @@ public class MainActivity extends Activity {
                         String rollbackStatus = "FAILED";
                         if (rollbackStatusCode == RollbackManager.STATUS_SUCCESS) {
                             rollbackStatus = "SUCCESS";
+                            mTriggerRollbackButton.setClickable(false);
                         }
                         makeToast("Status for rollback ID " + rollbackId + " is " + rollbackStatus);
                     }}, new IntentFilter(ACTION_NAME), Context.RECEIVER_NOT_EXPORTED);