Remove "usage:" prefix from usage messages

This is already added in by riak_cli. My eyes just scanned right over it
and I never realized until AJS pointed it out.
Switch to use riak_cli_typecast:to_node for safety
Fix indentation in riak_core_handoff_cli
Use riak_cli_status:text for command results

This is to accommodate the new riak_cli changes. Also I added some new
status messages for extra clarity while I was in there.
Break up lines >100 characters long
Fix possible spurious failure in handoff mgr test

Thanks to AJS for the idea on how to fix this.
Fix dialyzer warning due to change in riak_cli

riak_cli:register_node_finder used to return ok, but now it returns
true.