As QEMU becomes more multi-threaded and non-synchronized, checkpoints
move from thread to thread. And the event queue that processed at checkpoints
should belong to the same thread in both record and replay executions.
This patch disables asynchronous event processing at virtual clock
checkpoint, because it may be invoked in different threads at record and
replay. This patch is temporary fix until the checkpoints are completely
refactored.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <20181018063345.7433.11678.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>