Initialize hashrings as AgentManager object
Initialize hashrings as AgentManager object

If partition_coordinator value is valid, it will get hashrings. Before
that the object hashrings must be initialized.

Closes-Bug: #1716678
Change-Id: I3d2b67a70a67e2176dccf1c90f23c16a334c0fdf

openstack/ceilometer,openstack/ceilometer