nixos/release-small.nix: cleanup to use default versions

It makes more sense to test the packages, that probably more people are
using.

Changed files
+2 -3
nixos
+2 -3
nixos/release-small.nix
···
imagemagick
jdk
linux
-
mysql55
+
mysql
nginx
nodejs
openssh
php
-
postgresql92
-
postgresql93
+
postgresql
python
rsyslog
stdenv