Fix MockRequest.post to accept function_invocation_id parameter

Author: cgillum

tests/models/test_DurableOrchestrationClient.py

@@ -67,7 +67,8 @@ async def delete(self, url: str):
         assert url == self._expected_url
         return self._response
 
-    async def post(self, url: str, data: Any = None, trace_parent: str = None, trace_state: str = None):
+    async def post(self, url: str, data: Any = None, trace_parent: str = None,
+                   trace_state: str = None, function_invocation_id: str = None):
         assert url == self._expected_url
         return self._response