server: don't use SO_REUSEADDR socket option

After the dynamic worker count reconfiguration has been removed,
there is no need for SO_REUSEADDR option anymore.

src/contrib/net.c

@@ -166,6 +166,8 @@ static void unlink_unix_socket(const struct sockaddr_storage *addr)
 
 int net_bound_socket(int type, const struct sockaddr_storage *addr, enum net_flags flags)
 {
+	int ret;
+
 	/* Create socket. */
 	int sock = net_unbound_socket(type, addr);
 	if (sock < 0) {
@@ -177,13 +179,6 @@ int net_bound_socket(int type, const struct sockaddr_storage *addr, enum net_fla
 		unlink_unix_socket(addr);
 	}
 
-	/* Reuse old address if taken. */
-	int ret = sockopt_enable(sock, SOL_SOCKET, SO_REUSEADDR);
-	if (ret != KNOT_EOK) {
-		close(sock);
-		return ret;
-	}
-
 	/* Don't bind IPv4 for IPv6 any address. */
 	if (addr->ss_family == AF_INET6) {
 		ret = sockopt_enable(sock, IPPROTO_IPV6, IPV6_V6ONLY);