hw/s390x/s390-virtio-ccw: Fix a record/replay deadlock

hw/s390x/s390-virtio-ccw: Fix a record/replay deadlock

Booting an s390x VM in record/replay mode hangs due to a deadlock
between rr_cpu_thread_fn() and s390_machine_reset(). The former needs
the record/replay mutex held by the latter, and the latter waits until
the former completes its run_on_cpu() request.

Fix by temporarily dropping the record/replay mutex, like it's done in
pause_all_vcpus().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-ID: <20250124112625.23050-1-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>