devpi-server: fix tests
devpi-server: fix tests

Tests relied on a function that has no order guarantee. A fix was merged
to devpi master [1]. We point the package to this commit which should fix
the failing tests on hydra.

[1] https://github.com/devpi/devpi/pull/821

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs