Fix a few issues with 616-cha-unloading.

- Disable test on RI
- Disable test on trace
- Don't try N times for getting the allocation we want, do it
  until we get it. We shouldn't get in an infinite loop. If
  we do the harness will kill the test.

Test: 616-cha-unloading
bug: 73143991
Change-Id: I1eaf6db1a79010f1e5dc33401e5ccf351ff10be2
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 7292280..9f0f954 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -949,7 +949,17 @@
         ],
         "variant": "jvm",
         "bug": "b/73888836",
-        "description": ["Failing on JVM. Needs further investigating."]
+        "description": ["Failing on RI. Needs further investigating."]
+    },
+    {
+        "tests": ["616-cha-unloading"],
+        "variant": "jvm",
+        "description": ["Doesn't run on RI."]
+    },
+    {
+        "tests": ["616-cha-unloading"],
+        "variant": "trace",
+        "description": ["Trace prevents class unloading."]
     },
     {
         "tests": "677-fsi",