update no auth call flow

[mdr0id]

Update conditionals to allow no auth calls

[yrbb]

# searcher.py
def intercept_unary_stream(self, continuation, client_call_details, request):
        headers = []
        if self._kp != None:
            self.authenticate_if_needed()
            headers = [("authorization", f"Bearer {self._access_token.token}")]

        client_call_details = self._insert_headers(
            headers,
            client_call_details,
        )

        return continuation(client_call_details, request)
        
        
# async_searcher.py also needs fix