libnetwork/drivers/overlay: getBridgeNamePrefix() simplify reading of resolv.conf

We only need the content here, not the checksum, so simplifying the code by
just using os.ReadFile().

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/drivers/overlay/ov_network.go

@@ -531,8 +531,8 @@ func (n *network) getBridgeNamePrefix(s *subnet) string {
 func checkOverlap(nw *net.IPNet) error {
 	var nameservers []string
 
-	if rc, err := resolvconf.Get(); err == nil {
-		nameservers = resolvconf.GetNameserversAsCIDR(rc.Content)
+	if rc, err := os.ReadFile(resolvconf.Path()); err == nil {
+		nameservers = resolvconf.GetNameserversAsCIDR(rc)
 	}
 
 	if err := netutils.CheckNameserverOverlaps(nameservers, nw); err != nil {