init.d: fix return value

If program is dead but pid file exists (ret: 2) or the pidfile does
not exist (ret: 3), the init script return a non-zero value, yet
uchiwa starts fine.
Some configuration management tool  (Puppet here) expects a service
that started normally to return a 0 value. All non-zero value are
considered an error.

This patch aims to update the code return value to the latest possible
value, ie. the one returned by start.