BUGFIX: fix c931d60c

After c931d60c, default was "None" which means false.
But we want the default to be true. So use the special default argparse.SUPPRESS that removes totally the arg from arg dict.
It will let the default come from the FormatConfig class attribute.

slapos/cli/format.py

@@ -29,6 +29,7 @@
 
 import logging
 import sys
+import argparse
 
 from slapos.cli.command import check_root_user
 from slapos.cli.config import ConfigCommand
@@ -62,13 +63,13 @@ class FormatCommand(ConfigCommand):
 
         ap.add_argument('--alter_user',
                         choices=['True', 'False'],
-                        #default=FormatConfig.alter_user, #can't use default here because it would overwrite .cfg
+                        default=argparse.SUPPRESS, #can't use default here because it would overwrite .cfg
                         help='Shall slapformat alter user database'
                              ' (default: {})'.format(FormatConfig.alter_user))
 
         ap.add_argument('--alter_network',
                         choices=['True', 'False'],
-                        #default=FormatConfig.alter_network, #can't use default here because it would overwrite .cfg
+                        default=argparse.SUPPRESS, #can't use default here because it would overwrite .cfg
                         help='Shall slapformat alter network configuration'
                              ' (default: {})'.format(FormatConfig.alter_network))