Revert "Merge branch 'staging'" due to glibc

The main output started to retain dependency on bootstrap-tools; see
https://github.com/NixOS/nixpkgs/pull/15867#issuecomment-227949096

This reverts commit c05d829598, reversing
changes made to f073df60d6.

nixos/lib/testing.nix

@@ -113,14 +113,14 @@ rec {
             --add-flags "$vms" \
             ${lib.optionalString enableOCR "--prefix PATH : '${ocrProg}/bin'"} \
             --run "testScript=\"\$(cat $out/test-script)\"" \
-            --set testScript '$testScript' \
-            --set VLANS '${toString vlans}'
+            --set testScript '"$testScript"' \
+            --set VLANS '"${toString vlans}"'
           ln -s ${testDriver}/bin/nixos-test-driver $out/bin/nixos-run-vms
           wrapProgram $out/bin/nixos-run-vms \
             --add-flags "$vms" \
             ${lib.optionalString enableOCR "--prefix PATH : '${ocrProg}/bin'"} \
-            --set tests 'startAll; joinAll;' \
-            --set VLANS '${toString vlans}' \
+            --set tests '"startAll; joinAll;"' \
+            --set VLANS '"${toString vlans}"' \
             ${lib.optionalString (builtins.length vms == 1) "--set USE_SERIAL 1"}
         ''; # "