Add android.hardware.cts.SensorTest#testBatchAndFlush to knownfailures

Bug: 18958411
Change-Id: I088183d7127fa5efecc2e33ab9504e6a7648626a
diff --git a/tests/expectations/knownfailures.txt b/tests/expectations/knownfailures.txt
index 3b2e3f0..72a2811 100644
--- a/tests/expectations/knownfailures.txt
+++ b/tests/expectations/knownfailures.txt
@@ -322,6 +322,13 @@
   bug: 17675466
 },
 {
+  description: "tests will soon become mandatory",
+  names: [
+    "android.hardware.cts.SensorTest#testBatchAndFlush"
+  ],
+  bug: 18958411
+},
+{
   description: "This test failed on hw decoder that doesn't output frame with the configured format.",
   names: [
     "android.media.cts.ImageReaderDecoderTest#testHwAVCDecode360pForFlexibleYuv"