Revert "Temporarily disable chromium test"

This reverts commit 9e6eec201b8b56ef493c60af3acb2e8ddd8be258.

Verified locally that cd063d7 fixes the problem.
cc @edolstra @aszlig

nixos/release-combined.nix

···
         nixos.ova.x86_64-linux
 
         #(all nixos.tests.containers)
-        #nixos.tests.chromium
+        nixos.tests.chromium
         (all nixos.tests.firefox)
         (all nixos.tests.firewall)
         nixos.tests.gnome3.x86_64-linux # FIXME: i686-linux

nixos/release.nix

···
   tests.boot = callSubTests tests/boot.nix {};
   tests.boot-stage1 = callTest tests/boot-stage1.nix {};
   tests.cadvisor = hydraJob (import tests/cadvisor.nix { system = "x86_64-linux"; });
-  #tests.chromium = (callSubTests tests/chromium.nix { system = "x86_64-linux"; }).stable;
+  tests.chromium = (callSubTests tests/chromium.nix { system = "x86_64-linux"; }).stable;
   tests.cjdns = callTest tests/cjdns.nix {};
   tests.containers-ipv4 = callTest tests/containers-ipv4.nix {};
   tests.containers-ipv6 = callTest tests/containers-ipv6.nix {};