Bug#905772: libvirtd upgrade broken stretch->buster

[Sam Hartman]

control: severity -1 normal

Hi.  I ran a number of other upgrades today of libvirtd from stretch to
buster and was not able to reproduce the problem in the environments I
thought would cause it.
I don't know what's up, but I don't think characterizing this as RC
given the data we have is correct.