The bug could lead to data corruption (if a partition is wrongly marked as
UP_TO_DATE) or crashes (assertion failure on either the storage or the master).

The protocol is extended to handle the following scenario:

    S                                    M
    partition 0 outdated
      <-- UnfinishedTransactions ------>
    replication of partition 0 ...
    partition 1 outdated
      --- UnfinishedTransactions ...
    ... replication finished
      --- ReplicationDone ...
                                         tweak
      <-- partition 1 discarded --------
                                         tweak
      <-- partition 1 outdated ---------
          ... UnfinishedTransactions -->
          ... ReplicationDone --------->

The master can't simply mark all outdated cells as being updatable when it
receives an UnfinishedTransactions packet.