drm_hwcomposer: improve logging and reliability of some error paths

Change-Id: I4a955c6261a9674009eec2264eb2ef4a161da9c4
diff --git a/drmcompositor.cpp b/drmcompositor.cpp
index ad4cf88..b486d7b 100644
--- a/drmcompositor.cpp
+++ b/drmcompositor.cpp
@@ -76,7 +76,7 @@
     int ret = compositor_map_[display].QueueComposition(
         composition->TakeDisplayComposition(display));
     if (ret) {
-      ALOGE("Failed to queue composition for display %d", display);
+      ALOGE("Failed to queue composition for display %d (%d)", display, ret);
       return ret;
     }
   }