Add DestinationRegion if user does not provide the value

This will also fix the case where a user is not doing a copy
of an encrypted snapshot, because DestinationRegion is not required.
Update comments in tests to be accurate
Merge branch 'ebs-snapshot-dst-region' into develop

* ebs-snapshot-dst-region:
  Update comments in tests to be accurate
  Add DestinationRegion if user does not provide the value