Put the sed insert statement back in to the output.

Turns out that commit a369c883 (merged in PR #18368) make a bad change to modules/makeconf.py where it removed the insertion part of a '/regex/ i\text' construction.

salt/modules/makeconf.py

@@ -40,8 +40,10 @@ def _add_var(var, value):
     fullvar = '{0}="{1}"'.format(var, value)
     if __salt__['file.contains'](makeconf, layman):
         # TODO perhaps make this a function in the file module?
-        cmd = ['sed', '-i', '/{0}/'.format(layman.replace('/', '\\/')),
-               fullvar, makeconf]
+        cmd = ['sed', '-i', '/{0}/ i\{1}'.format(
+                    layman.replace('/', '\\/'),
+                    fullvar),
+               makeconf]
         __salt__['cmd.run'](cmd)
     else:
         __salt__['file.append'](makeconf, fullvar)