Drivers: hv: vmbus: Fix a bug in channel rescind code

Rescind of subchannels were not being correctly handled. Fix the bug.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org>        [3.11+]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>