discover/grub2: Allow to separate the --id argument using a space char

[petitboot] / test / urls / data / ipv6-noport.test

http://[1080:0:0:0:8:800:200C:417A]/index.html
scheme  http
host    1080:0:0:0:8:800:200C:417A
port    (null)
path    /index.html
dir     /
file    index.html