JCLOUDS-607: ComputeService.createNodesInGroup throws NPE on FloatingIPA...

Addresses possible returned null value from 'FloatingIPApi.create()'. If upon check we find null then throw InsufficientResourcesException. This in turn will make a second check at IP allocation by iterating through 'FloatingIPApi.list()' and grabbing an available IP. If this subsequent call fails then re-throw InsufficientResourcesException.
Please use a 3-space indent and spaces around the condition:
```
if (ip == null) {
   throw new...
}
```
Also, if the IRE allows you to pass a message, please pass one, e.g. "Unable to create floating IP for node + ..." or so?