datapath-windows: Re-init the list entry in OvsDeleteVportCmdHandler().

Without this patch, the kernel crashes when it tries to cleanup a port
at unload time when a port has been previously deleted from userspace.
Crash is in OvsRemoveAndDeleteVport() when we call into
RemoveEntryList().

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Tested-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>