empty_buckets: Remove vestigial per_host reserved word, improved per_type parameter value check.
empty_buckets: Remove vestigial per_host reserved word, improved per_type parameter value check.

Solinea/goldstone-server,slashk/goldstone-server,slashk/goldstone-server,Solinea/goldstone-server,slashk/goldstone-server,slashk/goldstone-server,slashk/goldstone-server,Solinea/goldstone-server,Solinea/goldstone-server,Solinea/goldstone-server