When adding new storage capacity, its desirable to disable ring
rebalancing until all new storage has been added, allowing the
end-user to determing when all new capacity has been added and its
OK to rebalance the rings and re-distribute.
Ensure that storage hook events from swift-storage observe the
'disable-ring-rebalance' configuration option, enabling end users
to perform this type of orchestration storage expansion.
Change-Id: I95727e663b369d5feb28147b19edcc6cab36b905
Closes-Bug: 1638981
1cf5ea71d0