Update git submodules

* Update plugins/replication from branch 'master'
  to 4786c07027a0040810ae3e6a517f737cb57e1283
  - Prune non-waiting tasks from queue during distribution
    
    Make the replication distributor also prune the tasks which have been
    removed from the persistent waiting directory but that are still in the
    queue. Since these tasks are not in the waiting directory, they will not
    run once they could run anyway. Cleaning these tasks up gives a more
    accurate picture of the replication work still needing to be done.
    Presumably these tasks have been removed externally by another actor
    (likely because they completed on another master in the cluster). This
    keeps the scheduled and waiting lists approximately synchronized across
    all the nodes in a multi-master cluster.
    
    Change-Id: If99ed75041fa07632fdc0f23473dad4d8942a3e1
    
  - Add a replication distributor
    
    The distributor schedules everything from the persistent waiting list
    every replication.distributionInterval so that replication can act on
    externally written tasks (likely by other nodes in the cluster). The
    interval defaults to 0, off.
    
    Change-Id: I8d7799b3a6f3f5362561fc593e52628ec2de51d4
    
diff --git a/plugins/replication b/plugins/replication
index 5622267..4786c07 160000
--- a/plugins/replication
+++ b/plugins/replication
@@ -1 +1 @@
-Subproject commit 5622267e9fe339e185c6e80978b57100476d8f25
+Subproject commit 4786c07027a0040810ae3e6a517f737cb57e1283