Disable flaky test

Test: this
Change-Id: I3dd39c4b774964ec6513601f520667db4870436a

libs/hwui/tests/unit/CommonPoolTests.cpp

@@ -54,7 +54,9 @@ TEST(DISABLED_CommonPool, threadCount) {
     EXPECT_EQ(0, threads.count(gettid()));
 }
 
-TEST(CommonPool, singleThread) {
+// Disabled since this is flaky. This isn't a necessarily useful functional test, so being
+// disabled isn't that significant. However it may be good to resurrect this somehow.
+TEST(CommonPool, DISABLED_singleThread) {
     std::mutex mutex;
     std::condition_variable fence;
     bool isProcessing = false;