test: unset MAKEFLAGS from parent environment

Our test infrastructure inherits MAKEFLAGS=-j12 which cause test for
make-targets ( which does `make install install-lib` ) to output sometimes:

    installing patched package
    installing patched package-lib

and sometimes

    installing patched package-lib
    installing patched package

because with such MAKEFLAGS the order in which these two independent
targets are installed is not stable.

slapos/recipe/cmmi/tests.py

@@ -23,6 +23,7 @@ optionflags = (doctest.ELLIPSIS |
 
 
 def setUp(test):
+    os.environ.pop('MAKEFLAGS')
     zc.buildout.testing.buildoutSetUp(test)
     zc.buildout.testing.install('slapos.recipe.build', test)
     zc.buildout.testing.install_develop('slapos.recipe.cmmi', test)