Switch hspace defaults to the cluster policy

This changes from the current hardcoded defaults to the cluster
policy. The command line options now override the defaults from the
cluster, and the tiered spec mode is always enabled.

Also fixes a tiny typo in the man page (together with the man page
updates).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>