changed to allow extending libcloud drivers

Notice that in drivers/joyent.py , our methods can be called sc_start_node so that it does not clash with their base &lt;action&gt;_node or ex_&lt;action&gt;_node. However, as long as they are not private members, ours would naturally override their version of it.

I have tested the joyent code and all the base functions and the extended functions work perfectly.