lxd/network/driver/ovn: Updated client.LogicalSwitchPortSetDNS usage
lxd/network/driver/ovn: Updated client.LogicalSwitchPortSetDNS usage

Moves dynamic switch port IP detection into InstanceDevicePortSetup.
Makes it more efficient for pure-static IP setups as we then don't need to ask OVN for dynamic IPs.
Makes DNS name IPs dependent on DHCP being enabled for that protocol (as OVN allocates IP on port even if DHCP not enabled).

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

stgraber/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,lxc/lxd