Hide output of curl when getting the server ip

[MiguelNdeCarvalho]

Hey,
This comit will hide the curl output from the wireguard container logs.
What appears in the logs:

**** Server mode is selected ****
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    14  100    14    0     0     35      0 --:--:-- --:--:-- --:--:--    35
**** SERVERURL var is either not set or is set to "auto", setting external IP to auto detected value of x.x.x.x ****

Thanks,
Miguel de Carvalho

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