GH-133 Remove Clusters that only contain Clusters

Currently only Clusters that contains single cluster are removed.

Fixes GH-133

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #134 from GordonSmith/GH-133

GH-133 Remove Clusters that only contain Clusters

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>