mon: fix syntax error in osd pool create args

Just missing a space between pgp_num and properties specification.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Merge pull request #585 from ceph/wip-osd-pool-create-syntax

fix ceph tool (syntax error in command specification prevents anything from working)

Reviewed-by: Sage Weil <sage@inktank.com>