[20.09] networkmanager: 1.26.6 -> 1.26.8

[mweinelt]

Motivation for this change

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NetworkManager-1.26.8
Overview of changes since NetworkManager-1.26.6
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* Fix delay in activating Wi-Fi connections after wake-up.
* Fix configuring a large number of allowed-ips on WireGuard link.
* cloud-setup: fix replacing IPv4 addresses during update.
* initrd: apply the MTU from bond= argument to the bond connection.
* initrd: add support for rd.net.timeout.carrier.
* Fix crash evaluating match setting properties (CVE-2021-20297).
* Various minor fixes.

Fixes: CVE-2021-20297

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.