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 started fine.
Some configuration management (Puppet here) tool 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.
Ensure uchiwa runs with additional sensu group

`uchiwa` user is created as part of `uchiwa` and `sensu` group, but when using chroot with only `--userspec` it will make it run only as part of the `uchiwa` group. This means no access to the `sensu` accessible `/etc/sensu` directory. As such it will not be able to read the configuration file in `/etc/sensu/uchiwa.js`.
Merge pull request #6 from Mylezeem/fix_ret_value

init.d: fix return value
Merge pull request #7 from JonathanTron/master

Ensure uchiwa runs with additional sensu group