dns: small refactor to setEDNS to return early

Using a guard clause instead of a long nested if.

The diff is best viewed with whitespace turned off.

agent/dns.go

@@ -273,8 +273,11 @@ func (d *DNSServer) ReloadConfig(newCfg *config.RuntimeConfig) error {
 // possibly the ECS headers as well if they were present in the
 // original request
 func setEDNS(request *dns.Msg, response *dns.Msg, ecsGlobal bool) {
-	// Enable EDNS if enabled
-	if edns := request.IsEdns0(); edns != nil {
+	edns := request.IsEdns0()
+	if edns == nil {
+		return
+	}
+
 	// cannot just use the SetEdns0 function as we need to embed
 	// the ECS option as well
 	ednsResp := new(dns.OPT)
@@ -301,7 +304,6 @@ func setEDNS(request *dns.Msg, response *dns.Msg, ecsGlobal bool) {
 
 	response.Extra = append(response.Extra, ednsResp)
 }
-}
 
 // recursorAddr is used to add a port to the recursor if omitted.
 func recursorAddr(recursor string) (string, error) {