[OpenAFS] -hr option to fileserver, IP address-based ACL delay

[Jeff Blaine]

We'd like IP address-based ACLs to go live sooner than they do by
default.

   -hr <number of hours between refreshing the host cps>

   Specifies how often the File Server refreshes its knowledge
   of the machines that belong to protection groups (refreshes
   the host CPSs for machines). The File Server must update
   this information to enable users from machines recently
   added to protection groups to access data for which those
   machines now have the necessary ACL permissions.

What's the default value?

Is there anything I need to know about setting this?  Obviously
it's not something one wants to do frequently because its argument
is in *hour* units.  Why not?