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
diff --git a/partitionmanager.cpp b/partitionmanager.cpp
index 0b3881e..72bd197 100755
--- a/partitionmanager.cpp
+++ b/partitionmanager.cpp
@@ -1594,7 +1594,7 @@
 		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();