[autotest] Simplify direct_afe proxy logic

BUG=chromium:672727
TEST=None

Change-Id: Idcc9627e5c53a0348ceb58b00b13afc000d8f16e
Reviewed-on: https://chromium-review.googlesource.com/436564
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/frontend/afe/direct_afe.py b/frontend/afe/direct_afe.py
index aecae61..60f96c2 100644
--- a/frontend/afe/direct_afe.py
+++ b/frontend/afe/direct_afe.py
@@ -14,14 +14,5 @@
     making RPC calls to an RPC server.
     """
     def run(self, call, **dargs):
-        func = None
-
-        try:
-            func = rpc_interface.__getattribute__(call)
-        except AttributeError:
-            pass
-
-        if not func:
-            raise AttributeError('No function %s in rpc_interface' % call)
-
+        func = rpc_interface.__getattribute__(call)
         return func(**dargs)