Get key from configuration if not exists on backend class

Author: rathishcholarajan

qiskit_ibm_runtime/ibm_backend.py

@@ -114,7 +114,11 @@ def __getattr__(self, name: str) -> Any:
             )
         try:
             return super().__getattribute__(name)
-        except KeyError:
+        except AttributeError:
+            pass
+        try:
+            return self._configuration.__getattribute__(name)
+        except AttributeError:
             raise AttributeError(
                 "'{}' object has no attribute '{}'".format(
                     self.__class__.__name__, name