Fixes #6056 - HC override desc create/update sysid

Override host-collection create/update's description for --system-ids so
that it asks the user for ids.
also, we use slightly different wording between the description of --system-ids on the 'add-content-host' and 'update' commands... i wonder it might be good to make them more consistent...

e.g.
add-content-host uses:
Array of system ids
update uses:
List of system ids to replace the content hosts in host collection

Perhaps just change 'List' to 'Array'.  Sorry for the nitpick... ;)