BUG/MINOR: dns: Fix SRV records with the new thread code.

srv_set_fqdn() may be called with the DNS lock already held, but tries to
lock it anyway. So, add a new parameter to let it know if it was already
locked or not;
diff --git a/include/proto/server.h b/include/proto/server.h
index ff4ec77..14f4926 100644
--- a/include/proto/server.h
+++ b/include/proto/server.h
@@ -56,7 +56,7 @@
 
 /* functions related to server name resolution */
 int snr_update_srv_status(struct server *s, int has_no_ip);
-const char *update_server_fqdn(struct server *server, const char *fqdn, const char *updater);
+const char *update_server_fqdn(struct server *server, const char *fqdn, const char *updater, int dns_locked);
 int snr_resolution_cb(struct dns_requester *requester, struct dns_nameserver *nameserver);
 int snr_resolution_error_cb(struct dns_requester *requester, int error_code);
 struct server *snr_check_ip_callback(struct server *srv, void *ip, unsigned char *ip_family);