test: Fix issues with check-terminal on Debian
test: Fix issues with check-terminal on Debian

If we boot fast, and the hostname is not yet set, then there's
a chance that the test will see alternate characters at the
terminal boot prompt.

Closes #3802
Reviewed-by: Peter <a316049dd34607c62d4611d63ab22a6454add223@redhat.com>

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