Exit code for No players found

[avidseeker]

When no player is found, playerctl should exit with an exit code different than 0.

    if (!one_selected && !no_status_error_messages) {
        g_printerr("No players found\n");
        return 2;
    }

This is so that playerctl can be used in script as follows

playerctl -l && playerctl metadata title

instead of directly having

playerctl metadata title

which results in scripts spamming stderr with No players found