Make sure FDs are closed before spawning subprocesses

This is not the default with Python 2.

slapos/recipe/cmmi/__init__.py

@@ -262,7 +262,7 @@ class Recipe(object):
         """Run the given ``cmd`` in a child process."""
         log = logging.getLogger(self.name)
         try:
-            retcode = subprocess.call(cmd, shell=True, env=self.augmented_environment())
+            retcode = subprocess.call(cmd, shell=True, env=self.augmented_environment(), close_fds=True)
 
             if retcode < 0:
                 log.error('Command received signal %s: %s' % (-retcode, cmd))