Drivers: hv: vmbus: Fix the offer_in_progress in vmbus_process_offer()

I didn't really hit a real bug, but just happened to spot the bug:
we have decreased the counter at the beginning of vmbus_process_offer(),
so we mustn't decrease it again.

Fixes: 6f3d791f ("Drivers: hv: vmbus: Fix rescind handling issues")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Stable <stable@vger.kernel.org> # 4.14 and above
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>