net: Fix data-races around sysctl_fb_tunnels_only_for_init_net.
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.64 by commit 181bae6dff66401a2fee4345242ed8a760493a62, it was introduced in version v4.17 by commit 79134e6ce2c9d1a00eab4d98cb48f975dd2474cb. For more details please see the references link.