Update git submodules
Update git submodules

* Update plugins/replication from branch 'stable-2.16'
  to d4981a1921e48fe76d97f7cc6107ae074879bfbe
  - Store replication tasks instead of ref-update events
    
    Fix the granularity of persistent events on disk by storing
    replication tasks rather than ref-update events.
    
    Ref-updates are triggering the replication tasks,
    however it is tricky to perform reference counting on the associated
    tasks reliably, due to all the different conditions of where a
    replication task can be in the replication queue.
    
    Fix a recurring issue on the persistence of ref-update events.
    The persisted ref-update events were either removed prematurely on the
    filesystem or left forever orphan even after the replication was completed
    on all remotes and target URLs.
    The problem was caused by the different granularity of the incoming
    ref-update events and the corresponding replication tasks queued
    and executed.
    
    Do not persist ref-update events anymore but include remote and
    target URLs at the replication tasks and persist those instead.
    
    The stored objects are replication tasks and not anymore ref-update
    events.
    
    Bug: Issue 11172
    Change-Id: I02d8cda0a124e8e3d2b9bb01b7d44f98ba717fcd
    
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