Avoid machine name ending in "-"

- can cause invalid name when jclouds appends "-id", by having
  two hyphens in a row
Fix JcloudsLocation user-setup

- in https://github.com/brooklyncentral/brooklyn/pull/1082
  a superset of these changes were done in master
Merge pull request #1102 from aledsage/fix/jclouds-for-t24

Fix/jclouds for t24