setup sftp correctly on RedHat-like machines

openssh/map.jinja

@@ -73,6 +73,9 @@ that differ from whats in defaults.yaml
     'Arch': {
         'Subsystem': 'sftp /usr/lib/ssh/sftp-server',
     },
+    'RedHat': {
+        'Subsystem': 'sftp /usr/libexec/openssh/sftp-server',
+    },
     'default': {}
   }
   , grain="os_family"