crush: return -1 on error from get_type_id

So we can distinguish between a bad type name and type 0.

Fix both callers, too.

Signed-off-by: Sage Weil <sage@inktank.com>
mon: generate useful error msgs for 'osd crush rule create-simple ...'

Signed-off-by: Sage Weil <sage@inktank.com>
ceph: add 'osd crush rule ...' to usage

Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #254 from ceph/wip-crush-rules

Reviewed-by: Joao Luis <joao.luis@inktank.com>