Comment 2 for bug 1854126

this is because if instance cpu model is none, it will check host info, but for host info
saw this log indicate that host calculation is not support at host side

2019-11-27 11:54:49.636 21154 INFO nova.virt.libvirt.driver [req-268522df-c953-4b92-8770-7f3528984e06 - - - - -] URI qemu:///system does not support full set of host capabilities: this function is not supported by the connection driver: cannot compute baseline CPU of s390x architecture