THRIFT-3906 Run C# tests with make check

This closes #1069
diff --git a/test/tests.json b/test/tests.json
index 3938c57..0dbc8bf 100644
--- a/test/tests.json
+++ b/test/tests.json
@@ -331,7 +331,7 @@
   {
     "name": "csharp",
     "env": {
-      "MONO_PATH": "../.."
+      "MONO_PATH": "../../lib/csharp/"
     },
     "transports": [
       "buffered",
@@ -361,7 +361,7 @@
         "client"
       ]
     },
-    "workdir": "../lib/csharp/test/ThriftTest"
+    "workdir": "csharp"
   },
   {
     "name": "perl",