debian: Re-add --timeout option for ifupdown script.

Commit fba6bd1d3f(ovs-vsctl: Try connecting only once for active connections..)
removed the timeout option from ifupdown.sh. Removing the "--timeout=" option
can cause ifupdown script to hang if ovs-vswitchd is not running and ifupdown
script changes the OVSDB. So, re-add it.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>