Mark bionic-stress-test as not unit tests as it run forever

This timed out the invocation when trying to run all cc_test, excluding it from unit tests.

Change-Id: I67758d5e49b607b7c10052bc193d885d9123bedf
Test: presubmit
Bug: 179092189
diff --git a/tests/Android.bp b/tests/Android.bp
index a6a930e..bf78f50 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -1017,6 +1017,10 @@
 
     // For now, these tests run forever, so do not use the isolation framework.
     isolated: false,
+    // Running forever, do not consider unit test.
+    test_options: {
+        unit_test: false,
+    },
 
     srcs: [
         "malloc_stress_test.cpp",