Check for VAB flag before calling UpdateUsesCompression

On a device which doen't support VAB, calligng UpdateUsesCompression
directly will cause libsnapshot to print error logs. Therefore check for
VAB support first.

Test: th
Change-Id: Icfbf848908939069493f6c10f6a69f022b9b8350
diff --git a/aosp/dynamic_partition_control_android.cc b/aosp/dynamic_partition_control_android.cc
index ab349a8..93a10bb 100644
--- a/aosp/dynamic_partition_control_android.cc
+++ b/aosp/dynamic_partition_control_android.cc
@@ -1470,7 +1470,8 @@
 }
 
 bool DynamicPartitionControlAndroid::UpdateUsesSnapshotCompression() {
-  return snapshot_->UpdateUsesCompression();
+  return GetVirtualAbFeatureFlag().IsEnabled() &&
+         snapshot_->UpdateUsesCompression();
 }
 
 }  // namespace chromeos_update_engine