datapath-windows: Removed duplicate checking of previous dump state

Removed the check for previous dump state before calling FreeUserDumpState
as the check is also performed in the latter function.

Signed-off-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>