SF: avoid calling pendingBuffers.insert twice

ag/13806579 accidently added another call to pendingBuffers.insert which
is incorrect.

Bug: 181978893
Test: SF unit tests
Change-Id: I3e7df528f8dcb1ccd8c5a83c51b23b8433a049d3
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 3b0e594..7706ad5 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3412,7 +3412,7 @@
         const auto vsyncId = frameTimelineInfoChanged ? s.frameTimelineInfo.vsyncId : info.vsyncId;
         if (isAutoTimestamp && layer->frameIsEarly(expectedPresentTime, vsyncId)) {
             ATRACE_NAME("frameIsEarly()");
-            return false;
+            ready = false;
         }
 
         if (!mScheduler->isVsyncValid(expectedPresentTime, layer->getOwnerUid())) {
@@ -3430,7 +3430,6 @@
             }
             pendingBuffers.insert(s.surface);
         }
-        pendingBuffers.insert(s.surface);
     }
     return ready;
 }