ResetStatus deletes snapshots for VAB.

When ResetStatus() is called, delete snapshots to free up space on
VAB devices.

On regular A/B, there is no need to cancel the update completely so that
the update may be resumed next time. However, on VAB devices, a
cancelled update should not occupy previously allocated space.

Test: manually call update_engine_client --cancel when an update is in progress, then
      call update_engine_client --reset_status, then
      call snapshotctl dump to check that snapshots are deleted.
      Then, re-apply the update.

Test: manually kill update_engine when an update is in progress, then
      call update_engine_client --reset_status, then
      call snapshotctl dump to check that snapshots are deleted.
      Then, re-apply the update.

Test: manually apply an update until UPDATED_NEED_REBOOT, then
      call update_engine_client --reset_status, then
      call snapshotctl dump to check that snapshots are deleted.
      Then, re-apply the update.

Test: manually apply an update until UPDATED_NEED_REBOOT, then
      kill update_engine, then
      call update_engine_client --reset_status, then
      call snapshotctl dump to check that snapshots are deleted.
      Then, re-apply the update.

Bug: 147696014

Change-Id: Ic7049772091a34e0e666fd7ae361ef474d5a28aa
Merged-In: Ic7049772091a34e0e666fd7ae361ef474d5a28aa
diff --git a/dynamic_partition_control_android_unittest.cc b/dynamic_partition_control_android_unittest.cc
index 4b1870d..457ea10 100644
--- a/dynamic_partition_control_android_unittest.cc
+++ b/dynamic_partition_control_android_unittest.cc
@@ -24,6 +24,7 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
+#include "update_engine/common/mock_prefs.h"
 #include "update_engine/dynamic_partition_test_utils.h"
 #include "update_engine/mock_dynamic_partition_control.h"
 
@@ -751,4 +752,9 @@
   EXPECT_FALSE(dynamicControl().OptimizeOperation("bar", iop, &optimized));
 }
 
+TEST_F(DynamicPartitionControlAndroidTest, ResetUpdate) {
+  MockPrefs prefs;
+  ASSERT_TRUE(dynamicControl().ResetUpdate(&prefs));
+}
+
 }  // namespace chromeos_update_engine