Copy queries prior to packing them in resolvers (#290)

* Copy queries prior to packing them in resolvers

* Fix race in quic restart logic

* Remove bad lock

dnsclient.go

@@ -65,6 +65,9 @@ func NewDNSClient(id, endpoint, network string, opt DNSClientOptions) (*DNSClien
 
 // Resolve a DNS query.
 func (d *DNSClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+	// Packing a message is not always a read-only operation, make a copy
+	q = q.Copy()
+
 	logger(d.id, q, ci).WithFields(logrus.Fields{
 		"resolver": d.endpoint,
 		"protocol": d.net,