do not map partitions on A/B devices

For pure AB devices(no VAB), MapAllPartitions() should not be called

Test: th
Bug: 393082101
Change-Id: I3ad44acb83d34d457a05ac8a165604afc19c150f
diff --git a/payload_consumer/postinstall_runner_action.cc b/payload_consumer/postinstall_runner_action.cc
index 1717dd7..84237b1 100644
--- a/payload_consumer/postinstall_runner_action.cc
+++ b/payload_consumer/postinstall_runner_action.cc
@@ -111,12 +111,17 @@
   // If we are switching slots, then we are required to MapAllPartitions,
   // as FinishUpdate() requires all partitions to be mapped.
   // And switching slots requires FinishUpdate() to be called first
-  if (!install_plan_.partitions.empty() ||
-      install_plan_.switch_slot_on_reboot) {
-    if (!dynamic_control->MapAllPartitions()) {
-      LOG(ERROR) << "Failed to map all partitions, this would cause "
-                    "FinishUpdate to fail. Abort early.";
-      return CompletePostinstall(ErrorCode::kPostInstallMountError);
+  if (dynamic_control->GetVirtualAbFeatureFlag().IsEnabled()) {
+    // If we are switching slots, then we are required to MapAllPartitions,
+    // as FinishUpdate() requires all partitions to be mapped.
+    // And switching slots requires FinishUpdate() to be called first
+    if (!install_plan_.partitions.empty() ||
+        install_plan_.switch_slot_on_reboot) {
+      if (!dynamic_control->MapAllPartitions()) {
+        LOG(ERROR) << "Failed to map all partitions, this would cause "
+                      "FinishUpdate to fail. Abort early.";
+        return CompletePostinstall(ErrorCode::kPostInstallMountError);
+      }
     }
   }