replay: don't synchronize memory operations in replay mode

Commit 9458a9a1 added synchronization
of vCPU and migration operations through calling run_on_cpu operation.
However, in replay mode this synchronization is unneeded, because
I/O and vCPU threads are already synchronized.
This patch disables such synchronization for record/replay mode.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@gmail.com>