This deprecates HostingServiceAccount.objects.accessible()'s

filter_local_site option, which was sort of an inverse of the

show_all_local_sites option that some other managers had.
With the introduction of LocalSite.ALL, we no longer need these

secondary flags. This change emits a deprecation warning if this flag is

set, and then converts to LocalSite.ALL if appropriate.

All unit tests pass.