Adding args and kwargs to oauth decorator in appengine (#4350)

### Motivation 

#4312 added the oauth handler to several get endpoints, in order for GCP
uptime to probe them. However, the decorator assumed that all handlers
would be of the form func(self), not declaring args or kwargs.

This is not true, for the following signatures:
```
coverage_report.py
...
  def get(self, report_type=None, argument=None, date=None, extra=None):
  
fuzzer_stats.py
...
  def get(self, extra=None):
```

This PR adds *args and **kwargs to the wrapper, so it can work for these
endpoints.

Part of #4271 

Error groups:

[coverage](https://pantheon.corp.google.com/errors/detail/CKrE1Jfd88vKIQ;service=;version=;filter=%5B%22handler%22%5D;time=P7D;locations=global?e=-13802955&inv=1&invt=AbfeYw&mods=logs_tg_prod&project=clusterfuzz-external)

[stats](https://pantheon.corp.google.com/errors/detail/CMiEwKaYs4DfEA;service=;version=;filter=%5B%22handler%22%5D;time=P7D;locations=global?e=-13802955&inv=1&invt=AbfeYw&mods=logs_tg_prod&project=clusterfuzz-external)

src/appengine/libs/handler.py

@@ -248,20 +248,20 @@ def oauth(func):
   """
 
   @functools.wraps(func)
-  def wrapper(self):
+  def wrapper(self, *args, **kwargs):
     """Wrapper."""
     auth_header = request.headers.get('Authorization')
     if auth_header:
       email, returned_auth_header = get_email_and_access_token(auth_header)
       setattr(g, '_oauth_email', email)
 
-      response = make_response(func(self))
+      response = make_response(func(self, *args, **kwargs))
       response.headers[CLUSTERFUZZ_AUTHORIZATION_HEADER] = str(
           returned_auth_header)
       response.headers[CLUSTERFUZZ_AUTHORIZATION_IDENTITY] = str(email)
       return response
 
-    return func(self)
+    return func(self, *args, **kwargs)
 
   return wrapper