change default ceph to firefly
work around ceph not liking gaps in ruleset numbers
use new create-or-move command
no replica count higher than the node count
default to store a replica per rack instead of host
count all nodes, not just head nodes
Revert "default to store a replica per rack instead of host"

This reverts commit 724b3d778df1354eabed8ea12fb8c26587a5b9af.
default to store a replica per rack instead of host
parameterize the type of treenode ceph should disribute by
change default to rack, but keep host for laptop env
fix messed up indentation
get rid of hacks around default pool placement & size
migrate rack_name to node object
only count head or work nodes in get_all_nodes
Merge pull request #145 from pchandra/firefly

Change default ceph to firefly
Merge pull request #149 from pchandra/ceph-replicas

Fix crush rule to store per rack instead of host