qmp: don't emit the RESET event on wakeup from S3

QEMU is basically using reset logic when waking up from S3. This
causes the QMP RESET event to be emitted, which is wrong. Also,
the runstate checks done in reset are not necessary for S3 wakeup.

Fix this by untangling wakeup from reset logic and passing
VMRESET_SILENT to qemu_system_reset() to avoid emitting the RESET
event.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
