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
np. it only takes a little more time, yet I feel less dirty inside. Thanks
for the nudge!