[sf] make legacy frontend debug flag persistent

Legacy frontend is still the default but we enable the new
front end, we want to disable the legacy by default as well.

Change-Id: I04ec50e05e9022be6efe1f83f29783ef49b11023
Test: presubmit
Bug: 238781169
(cherry picked from commit b999a7b415ca336270201b1ad346114769e91368)
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 786706a..2c1e333 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -476,7 +476,7 @@
     mLayerLifecycleManagerEnabled =
             base::GetBoolProperty("persist.debug.sf.enable_layer_lifecycle_manager"s, false);
     mLegacyFrontEndEnabled = !mLayerLifecycleManagerEnabled ||
-            base::GetBoolProperty("debug.sf.enable_legacy_frontend"s, true);
+            base::GetBoolProperty("persist.debug.sf.enable_legacy_frontend"s, false);
 }
 
 LatchUnsignaledConfig SurfaceFlinger::getLatchUnsignaledConfig() {