Fixes #7144 - add/remove content-hosts fails

Temp fix until https://github.com/theforeman/hammer-cli/pull/138 can get in.

This --content-host-ids is not being treated as an array and is therefore 
being sent incorrectly through apipie. There is currently a bug with
apipie where the type for the params are not being reported correctly.
This is a temp fix until the apipie issue can be fixed.