Camera: Ensure correct error message for disconnected devices

After a device has been disconnected, should return consistent errors
to the caller if they invoke further device methods.

For API1, that's INVALID_OPERATION, and for API2, that's
ERROR_DISCONNECTED.

Change-Id: I0f3d889906a9818c0e03852702b146fd33c9e42a
Fixes: 27591189