vpnc-script: fix for Suse pre 11.1

vpnc-script: fix for Suse pre 11.1

To handle /etc/resolv.conf file, Suse Linux pre 11.1
uses /sbin/modify_resolvconf script.
The same parameter "-s <service>" have to be passed
to modify_resolvconf on both "modify" and "restore".

Original vpnc-script.in from vpnc project runs:
  /sbin/modify_resolvconf modify -s $SCRIPTNAME ...
  /sbin/modify_resolvconf restore -s vpnc  ...
with $SCRIPTNAME=="vpnc".

In this repository, vpnc-script.in has been converted
to vpnc-script. Doing this, the value $SCRIPTNAME has
changed from "vpnc" to "vpnc-script".
This breaks the "restore" and left /etc/resolv.conf
modified for the (already closed) VPN tunnel.

Replace "-s $SCRIPTNAME" with fixed value "-s vpnc".

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>