Exclude `lo` when determining MTU of host
Exclude `lo` when determining MTU of host

The MTU of the lo device is irrelevant for determining the host's
maximum MTU. Note that for the pattern used in this patch the `extglob`
shell option is required.

SUSE-Cloud/automation,SUSE-Cloud/automation,gosipyan/automation,aspiers/automation,SUSE-Cloud/automation,SUSE-Cloud/automation,aspiers/automation,gosipyan/automation,gosipyan/automation,aspiers/automation,aspiers/automation,gosipyan/automation