Random waits were used to avoid restart collisions. This change uses
distributed_wait based on modulo_distribution to calculate wait time
based on the modulo-nodes setting (or peer relations) and known-wait.
charm-helpers sync for module distribution helpers
Depends-On: I02c648cccc72d816beeec5546b6c7914d57c607a
Change-Id: Ic796c23e1bc560d461c674cbfadf8589380eb649
a68b912cf5