Comment 4 for bug 1772927

From the test history, this P8 node was tested with 4.15.0-21, which
mean that the deployment works with some version earlier than
4.15.0-21, and at least it can boot with 4.15.0-21 in the last cycle.

So it's a bit odd to me to see the deployment failure here, as it should
be deployed with working 4.15.0-21 from the last cycle.

And it's not the 4.15.0-23 in -proposed that's causing this this problem, the system was never boot with 4.15.0-21.