Just a quick correction and apologies, the actual issue is that http will not work, https will so I dont think this is a bug as such I think this is by design likely for security.
Looking at the man page for qemu-kvm it states http will work with examples given however only https works, my best guess from looking at the spec file from the srpm is that it has only been enabled in the centos qemu-kvm-ev with https:
except from spec file:
example working XML except:
I have tested this on a base install with the regular packages and can confirm that it works fine over https.
Thanks again and sorry for any confusion caused.