Fix problem with delegating builds to localhost due to nix-store not being in the PATH

Dependencies

• [2] AGRIAC2F Fix hydra-queue-runner PATH
• [3] ZYEFL36Q Ported/merged properties from the TUD configuration's hydra-module
• [4] EE5RRP3X hydra-module.nix: Make services require hydra-init
• [5] HRFFN34B Fix email notification
• [6] L62I7CPI Don't put ssmtp in hydra's paths
• [7] 2ANV36PB Hackery
• [*] D3MDJONY

Change contents

• replacement in hydra-module.nix at line 295
  [3.1588]→[2.0:81](∅→∅)
  − path = [ cfg.package pkgs.nettools pkgs.ssmtp pkgs.openssh pkgs.bzip2 ];
  [3.1588]

  [3.127]
  + path = [ cfg.package pkgs.nettools pkgs.ssmtp pkgs.openssh pkgs.bzip2 config.nix.package ];