Removes exception is sysctl file is missing

When syscl file was missing, sysctl module was complaining about it and
bailing out.
This behaviour prevents usage of /etc/sysctl.d directory, present in
some distributions.
This patch accepts a missing sysctl.conf file so sysctl.d directory can
be used.
However, it will bail out if the destination directory doesn't exist.

sysctl

@@ -158,11 +158,13 @@ def sysctl_check(current_step, **sysctl_args):
     # sysctl file exists and openable ?
     # TODO choose if prefered to use os.access() instead try/catch on open
     if current_step == 'before':
+        if not os.access(sysctl_args['sysctl_file'], os.W_OK):
             try:
-            f = open(sysctl_args['sysctl_file'])
+                f = open(sysctl_args['sysctl_file'],'w')
+                f.write('')
                 f.close()
             except IOError, e:
-            return 1, 'unable to open supplied sysctl.conf'
+                return 1, 'unable to create supplied sysctl file (directory missing)'
 
     # no smart checks at this step ?
     if sysctl_args['checks'] == 'none':