Upgrade jclouds to 1.7.2-ea-brooklyn.4

- was previously 1.7.2-ea-brooklyn.3
- this gives SoftLayer multi-disk support, amongst other things
Fix unsupported iterable.remove in BasicMachineDetails
Merge pull request #1292 from aledsage/update/jclouds-version

Update jclouds version to 1.7.2-ea-brooklyn.4