Fix regression in DeviceProxy.read_attributes_reply

Prior to 10.0.0, the read_attributes_reply method would not raise if an attribute it read raised. This behaviour is restored, and a new test was added to check it.

Note that read_attribute_reply (singular) will still raise an exception in this case. That is the same behaviour we had prior to 10.0.0.

Closes #706 (closed)