Up the version
mongos does not support enable_rest.

Do not allow it to be applied, in case enable_rest is turned on for all
nodes or as a default attribute setting.
Support installation of an arbiter on top of a config instance.

Can be installed by using:

node.set[:mongodb][:arbiter] = true
mongodb_instance "arbiter" do
  mongodb_type "mongod"
  port         node['mongodb']['arbiter_port']
  logpath      node['mongodb']['logpath']
  dbpath       node['mongodb']['dbpath'] + '/arbiter'
  enable_rest  node['mongodb']['enable_rest']
  smallfiles   node['mongodb']['smallfiles']
  replicaset   node
end
Stop and disable the default RPM-installed init.d/mongod service.

Previous code was referring to mongodb, where there was no such service.
Fail fatally if the replica configuration fails.

Log attempted configuration command and add ability to do a dryrun.