datapath-windows: Use local time for Inf2Cat

Issue: cannot build properly when local date differs from UTC date, see:
    https://connect.microsoft.com/VisualStudio/feedback/details/787203/driver-package-building-problem

Since Stampinf stamps the driver inf file with the local date set the Inf2Cat
to use local date as well.

Signed-off-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>