When we add new guest os, sometimes we missed the records in guest_os_hypervisor.
However, the guest disk model (virtio/ide) is determined by record in the table.
It causes the issue that some new guest os(eg Debian 8/9) uses e1000 instead of virtio nic, and ide disk instead of virtio disk.
To fix the issue permanantly, pass the guest os name in guest_os if the record for kvm is not found in guest_os_hypervisor.
Related commit:7ac9f00eeeb4cd37ec39efeba066e799b581b1a0