Allow chmod for non-root users

[stormshield-sylvaing]

Problem

We have a non-root program using a hybrid system for daemonisation, it must use the PID files created by Daemonize. The files need to be chowned to the user group, this is how it's made :

Daemonize::new()
        .pid_file("/path/to/file.pid")
        .chown_pid_file(true)
        .user(Uid::current().as_raw())
        .group("my_group_name")
        .umask(0o017); // Gives RW permissions to user and group

The program fails because it tries to setgid and setuid while it is run as non-root.

Solution

I added a boolean to skip setgid and setuid so we can run the program as non-root. By default, the boolean is set to true for retro-compatibility :

Daemonize::new()
        .pid_file("/path/to/file.pid")
        .chown_pid_file(true)
        .set_group_and_user_id(false) // Skip `setgid` and `setuid`, can be run as non-root
        .user(Uid::current().as_raw())
        .group("my_group_name")
        .umask(0o017);

Impact for existing code base

None. By default, daemonize works exactly the same.