qemu: Converting DHCP and ARP functions to domain conf

qemu: Converting DHCP and ARP functions to domain conf

QEMU driver has two functions: qemuGetDHCPInterfaces() and
qemuARPGetInterfaces() that are being used inside only one single
function. They can be turned into generic functions that other drivers
can use. This commit move both from QEMU driver tree to domain conf
tree.

Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>