test: wait for the "latest" systemd-bsod message

test: wait for the "latest" systemd-bsod message

Let's wait for the "latest" message systemd-bsod prints to the console
to appear, otherwise we might be too fast and take a console snapshot
before it contains all the information:

[   44.237788] testsuite-04.sh[1744]: + setterm --term linux --dump --file /tmp/console.dump
[   44.246089] systemd-bsod[1858]: QR code could not be printed, ignoring: Operation not supported
[   44.305692] testsuite-04.sh[1744]: + grep -aq 'The current boot has failed' /tmp/console.dump
[   44.308047] testsuite-04.sh[1744]: + grep -aq 'Service emergency message' /tmp/console.dump
[   44.311200] testsuite-04.sh[1744]: + grep -aq 'Press any key to exit' /tmp/console.dump
[   44.314359] testsuite-04.sh[1744]: + at_exit
[   44.315087] testsuite-04.sh[1744]: + local EC=1
[   44.315945] testsuite-04.sh[1744]: + [[ 1 -ne 0 ]]
[   44.316647] testsuite-04.sh[1744]: + [[ -e /tmp/console.dump ]]
[   44.318305] testsuite-04.sh[1744]: + cat /tmp/console.dump
[   44.319320] testsuite-04.sh[1871]:    The current boot has failed!
[   44.319970] testsuite-04.sh[1871]:    Service emergency message