tun: Don't call tunnel script on reconnect events

tun: Don't call tunnel script on reconnect events

If --script-tun is used, the vpnc_script is not invoked for pre-init,
connect, or disconnect events.  However, it is invoked on reconnect, and
this may confuse the tunnel script.

Add an extra check to script_config_tun() to make the reconnect behavior
consistent with the behavior of other events.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>