If instance name is not provided, make something up

[isaac-s]

If blueprint has no value for the name property, the instance comes up without a name tag at all.
This is not in line with our OpenStack plugin, where we assign <node_name>_<node_instance_id> as the server's name if a name had not been provided in the blueprint.

Our OpenStack plugin approach may or may not be optimal, but leaving the name tag completely missing doesn't sound like the right thing to do.

[EarthmanT]

#RD-2908