random-util: eat up bad RDRAND values seen on AMD CPUs
An ugly, ugly work-around for #11810. And no, we shouldn't have to do
this. This is something for AMD, the firmware or the kernel to
fix/work-around, not us. But nonetheless, this should do it for now.
Fixes: #11810
(cherry picked from commit 1c53d4a0)
(cherry picked from commit 29dda759)