drm_hwcomposer: Route release fence directly

Current release_fence merging logic doesn't make much sence, cleanup it.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/backend/Backend.cpp b/backend/Backend.cpp
index d7eb240..bd1855f 100644
--- a/backend/Backend.cpp
+++ b/backend/Backend.cpp
@@ -46,8 +46,10 @@
 
     bool testing_needed = !(client_start == 0 && client_size == layers.size());
 
+    AtomicCommitArgs a_args = {.test_only = true};
+
     if (testing_needed &&
-        display->CreateComposition(true) != HWC2::Error::None) {
+        display->CreateComposition(a_args) != HWC2::Error::None) {
       ++display->total_stats().failed_kms_validate_;
       client_start = 0;
       client_size = layers.size();