Inject script on boot (if available) for multiple instances #34
Description
The issue is about script injection on boot and multiple instance creatio and is partially related to the issue ow2-proactive/connector-iaas#47.
On Azure & OpenStack cloud, the acquireNode script can be injected on VM's boot.
In addition, when we have multiple instances to start, some optimizations are made inside connector-iaas' createInstance method to start multiple VMs/instances as fast as possible using SDK features.
The problem is that the scripts need to be customized with instanceTag/id and (according to the model issue of the connector-iaas project) this will force instances to start sequentially.
We thus need to find a way to customize the script for each instance to take advantage of clouds SDK's parallel VMs deployment features.