nix: mkBackend should propagate flask development variables
nix: mkBackend should propagate flask development variables

mozilla-releng/services,andrei987/services,garbas/mozilla-releng-services,andrei987/services,lundjordan/services,mozilla-releng/services,srfraser/services,mozilla-releng/services,srfraser/services,mozilla-releng/services,garbas/mozilla-releng-services,garbas/mozilla-releng-services,garbas/mozilla-releng-services,lundjordan/services,La0/mozilla-relengapi,andrei987/services,andrei987/services,La0/mozilla-relengapi,lundjordan/services,srfraser/services,lundjordan/services,La0/mozilla-relengapi,srfraser/services,La0/mozilla-relengapi