Static IP and MAC addresses are allowed in rootless CNI

Loosen some restrictions within specgen around rootless
containers - they can now set static IP and MAC addresses as long
as they are in a CNI network.

Fixes containers#7842

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

pkg/specgen/container_validate.go

@@ -30,7 +30,7 @@ func exclusiveOptions(opt1, opt2 string) error {
 // input for creating a container.
 func (s *SpecGenerator) Validate() error {
 
-	if rootless.IsRootless() {
+	if rootless.IsRootless() && len(s.CNINetworks) == 0 {
 		if s.StaticIP != nil || s.StaticIPv6 != nil {
 			return ErrNoStaticIPRootless
 		}