This removes the old reference to the nova-manage
command to refresh quota usage which no longer
applies since we started counting quotas in the
Pike release.
This replaces with a reference to the down-cell
known issue for counting quotas.
Change-Id: I2765f3ca3dc95345d4e4c4db43ac3dff4a509259
Adds a section in the admin guide with the config options related to
down cells.
Related to blueprint handling-down-cell
Change-Id: I6a6cc71e83896aaccd5dd98bc2ea024d6f22d528