Close fence fd when used.

Bug: 122655785

Test: launch chrome, run stopwatch over 10 mins
Change-Id: I7818fd307658b9277c5ec7f7d4cc0f012d71c793
diff --git a/system/hwc2/EmuHWC2.cpp b/system/hwc2/EmuHWC2.cpp
index 37466a1..3a53296 100644
--- a/system/hwc2/EmuHWC2.cpp
+++ b/system/hwc2/EmuHWC2.cpp
@@ -697,6 +697,7 @@
                         ALOGE("%s waited on fence %d for 3000 ms",
                             __FUNCTION__, fence);
                     }
+                    close(fence);
                 }
                 else {
                     ALOGV("%s: aquiredFence not set for layer %u",