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 * fix spurious PingAck timeout, a regression of ack-processing in bottom half
   (introduced with 9.2.0)
 * support merging of discards during resync even if the discard granularity
   of the backing device is larger than 128MiB
 * merged changes from the drbd-9.1 branch, including
  - fix a race that could result in connection attempts getting aborted
    with the message "sock_recvmsg returned -11"
  - rate limit messages in case the peer can not write the backing storage
    and it does not finish the necessary state transitions
  - reduced the receive timeout during connecting to the intended 5 seconds
    (ten times ping-ack timeout)
  - losing the connection at a specific point in time during establishing
    a connection could cause a transition to StandAlone; fixed that, so
    that it keeps trying to connect
  - fix a race that could lead to a fence-peer handler being called
    unexpectedly when the fencing policy is changed at the moment before
    promoting