Staging: hv: util: Fix a bug in kvp implementation

Staging: hv: util: Fix a bug in kvp implementation

The host gurantees that there can be only one kvp transaction active
against the guest. So, the transaction active state is needed only to
protect against spurious user level calls. The current code had a race
condition where the guest could prematurely return because the previous
transaction state was not cleared - this state was being cleared after
sending the response to the host and there was a window where the host
could notify the guest of a new transaction before the transaction active
state was properly set.
Also deal with the case when the user mode component
does not respond in a timely fashion correctly.
I would like to thank Long Li <longli@microsoft.com>
for identifying the problem.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Diagnosed-by: Long Li <longli@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>