test: Disable internet access in check-sosreport
test: Disable internet access in check-sosreport

This removes the default gateway and disables internet access
in the check-sosreport test. The goal is to remove races that
depend on responses from Red Hat servers.

Closes #5177
Reviewed-by: Peter <a316049dd34607c62d4611d63ab22a6454add223@redhat.com>

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