pbs client: deprecate namespaced parameters

pbs client: deprecate namespaced parameters

All existing callers for functions with namespaced parameters just
re-use the one that's passed in via the initial configuration already,
so there is no need for namespaced parameters currently.

If the need for one PBS client to handle multiple namespaces arises, a
set_namespace() function could be added, or the relevant functions
could take an additional parameter, either for just the namespace or
like $cmd_opts in restore_pxar().

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>