vab: correct default properties when vab is enabled

- do not show vab options in advanced
- do not perform merges when vab is disabled

Change-Id: I20997eca515600cb07fe896305b861ee9418c326

partitionmanager.cpp

@@ -1594,7 +1594,7 @@ int TWPartitionManager::Format_Data(void) {
 		metadata->UnMount(false);
 
 	if (dat != NULL) {
-		if (android::base::GetBoolProperty("ro.virtual_ab.enabled", true)) {
+		if (android::base::GetBoolProperty("ro.virtual_ab.enabled", false)) {
 #ifndef TW_EXCLUDE_APEX
 			twrpApex apex;
 			apex.Unmount();