Drivers: hv: util: kvp: Fix a rescind processing issue

Drivers: hv: util: kvp: Fix a rescind processing issue

BugLink: http://bugs.launchpad.net/bugs/1676635
KVP may use a char device to support the communication between
the user level daemon and the driver. When the KVP channel is rescinded
we need to make sure that the char device is fully cleaned up before
we can process a new KVP offer from the host. Implement this logic.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 5a66fecbf6aa528e375cbebccb1061cc58d80c84)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>