Minimal fix for 500 errors when create-policy tags are not an array

This is the absolutely minimal fix for the current failure -- a runtime Ruby
error about methods missing, or other similar oddities -- when the value of
the "tags" data in create-policy is not the type expected.

This makes no attempt to find and fix similar errors elsewhere, and is a
one-shot patch for the specific failure.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>