Inconsistent uuid generation in azure_arm

## Summary

Azure returns inconsistent casing of the resource groups name in the id string, resulting in different uuid's for the same node (depending on what calls you make).

## Detailed Information

When a node is created, the resource groups name in the id string is lower case. In subsequent calls, like in list_nodes(), for some reason Azure returns the resource groups name in upper case. This results in a different uuid from when create_node() is called. This also breaks wait_until_running(). Forcing the id string to lower case in _to_node() seems to resolve this issue.

I made the change here: https://github.com/foospidy/libcloud/commit/2682d1229466fa577d4360ababd650d777ea49f3

I'd be happy to submit a PR.

Empiece por localizar el método _to_node() del proveedor Azure ARM y compare cómo producen los IDs create_node() y list_nodes(). Verifique que las mayúsculas y minúsculas del resource-group ya no cambien el UUID de un nodo y que wait_until_running() funcione de forma coherente; use el commit referenciado como contexto y añada o actualice tests específicos si la estructura de tests del proveedor identifica una ubicación adecuada.

Escrito por el modelo de indexación a partir del texto del issue.