Fixes the issue with fn test and adds relevant test cases, fixes #650 (#651)

* Fixes the issue with fn test and adds relevant test cases, fixes #650
* Checking log size for invalid function
* Testing the invalid function logs a few time beforr quitting
* Disabling the test for now, linked to issue #653

test/tests/test_function_test/hello.js

@@ -0,0 +1,6 @@
+module.exports = async function (context) {
+    return {
+        status: 200,
+        body: "Hello, Fission!\n"
+    };
+}