coroutine-sleep: move timer out of QemuCoSleepState

This simplification is enabled by the previous patch.  Now aio_co_wake
will only be called once, therefore we do not care about a spurious
firing of the timer after a qemu_co_sleep_wake.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20210517100548.28806-5-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>