Rename fetch_status to fetch_power_state.
Rename fetch_status to fetch_power_state.

Return node state based on 'provisioningState' if fetch_power_state is False.
Update API documentation.

Signed-off-by: Quentin Pradet <d17611fde61d73f8de1b8b01bc47d446558ccd8e@apache.org>

apache/libcloud,ByteInternet/libcloud,erjohnso/libcloud,pquentin/libcloud,StackPointCloud/libcloud,andrewsomething/libcloud,Scalr/libcloud,StackPointCloud/libcloud,ByteInternet/libcloud,andrewsomething/libcloud,mistio/libcloud,Kami/libcloud,andrewsomething/libcloud,mistio/libcloud,erjohnso/libcloud,Kami/libcloud,Scalr/libcloud,Kami/libcloud,vongazman/libcloud,StackPointCloud/libcloud,ByteInternet/libcloud,pquentin/libcloud,erjohnso/libcloud,Scalr/libcloud,apache/libcloud,apache/libcloud,vongazman/libcloud,mistio/libcloud,vongazman/libcloud,pquentin/libcloud