Add field-access/modification to ti-stress.

These tests stress jvmti FieldAccess and FieldModification.

Test: ./test/testrunner/testrunner.py --host --field-stress -j40
Change-Id: Ie2ea91e165beed73f14e8aff0adb137becdccd01
diff --git a/test/knownfailures.json b/test/knownfailures.json
index b7f5d4c..d8786a8 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -511,7 +511,7 @@
             "645-checker-abs-simd",
             "706-checker-scheduler"],
         "description": ["Checker tests are not compatible with jvmti."],
-        "variant": "jvmti-stress | redefine-stress | trace-stress"
+        "variant": "jvmti-stress | redefine-stress | trace-stress | field-stress"
     },
     {
         "tests": [
@@ -550,7 +550,7 @@
             "981-dedup-original-dex"
         ],
         "description": ["Tests that require exact knowledge of the number of plugins and agents."],
-        "variant": "jvmti-stress | redefine-stress | trace-stress"
+        "variant": "jvmti-stress | redefine-stress | trace-stress | field-stress"
     },
     {
         "tests": [
@@ -585,6 +585,13 @@
     },
     {
         "tests": [
+            "004-ThreadStress"
+        ],
+        "description": "The thread stress test just takes too long with field-stress",
+        "variant": "jvmti-stress | field-stress"
+    },
+    {
+        "tests": [
             "031-class-attributes",
             "911-get-stack-trace"
         ],