net: dns: Avoid errors when DNS dispatcher is already registered

Skip error prints and extra DNS events if DNS dispatcher was already
registered.

Signed-off-by: Jukka Rissanen <[email protected]>
(cherry picked from commit c110331)

Author: jukkar

subsys/net/lib/dns/resolve.c

@@ -477,6 +477,10 @@ static int dns_resolve_init_locked(struct dns_resolve_context *ctx,
 		ret = register_dispatcher(ctx, &resolve_svc, &ctx->servers[i], local_addr,
 						  addr6, addr4);
 		if (ret < 0) {
+			if (ret == -EALREADY) {
+				goto skip_event;
+			}
+
 			NET_DBG("Cannot register dispatcher for %s (%d)",
 				ctx->servers[i].is_mdns ? "mDNS" : "DNS", ret);
 			goto fail;
@@ -491,6 +495,8 @@ static int dns_resolve_init_locked(struct dns_resolve_context *ctx,
 			net_mgmt_event_notify(NET_EVENT_DNS_SERVER_ADD, iface);
 		}
 
+skip_event:
+
 #if defined(CONFIG_NET_IPV6)
 		local_addr6.sin6_port = 0;
 #endif