JCLOUDS-774 inconsistent region and zone mappings.

It appears that the "jclouds.regions" whitelist is being ignored in ec2. This can cause the zone supply to come back as null. This fixes that.

https://issues.apache.org/jira/browse/JCLOUDS-774
I hate it because it is distracting, and if we looked closely and were
interested in efficiency, we'd kill the function on function on predicate
stuff way before being concerned about looping 5 region keys multiple
times. So.. I'm killing the bigger problem.