ceph-disk: fix prepare --help

[ghost]

Signed-off-by: Loic Dachary loic@dachary.org

[tchaikov]

before this change

$ ./ceph-disk/virtualenv/bin/ceph-disk prepare --help
Traceback (most recent call last):
  File "./ceph-disk/virtualenv/bin/ceph-disk", line 9, in <module>
    load_entry_point('ceph-disk', 'console_scripts', 'ceph-disk')()
  File "/home/kchai/dev/ceph/src/ceph-disk/ceph_disk/main.py", line 4591, in run
    main(sys.argv[1:])
  File "/home/kchai/dev/ceph/src/ceph-disk/ceph_disk/main.py", line 4526, in main
    args = parse_args(argv)
  File "/home/kchai/dev/ceph/src/ceph-disk/ceph_disk/main.py", line 4234, in parse_args
    args = parser.parse_args(argv)
  File "/usr/lib64/python2.7/argparse.py", line 1688, in parse_args
...
  File "/usr/lib64/python2.7/argparse.py", line 209, in format_help
    func(*args)
  File "/usr/lib64/python2.7/argparse.py", line 515, in _format_action
    help_text = self._expand_help(action)
  File "/usr/lib64/python2.7/argparse.py", line 601, in _expand_help
    return self._get_help_string(action) % params
TypeError: unsupported operand type(s) for %: 'tuple' and 'dict'

after this change

$ ./ceph-disk/virtualenv/bin/ceph-disk prepare --help
usage: ceph-disk prepare [-h] [--cluster NAME] [--cluster-uuid UUID]
                         [--osd-uuid UUID] [--dmcrypt]
                         [--dmcrypt-key-dir KEYDIR] [--fs-type FS_TYPE]
                         [--zap-disk] [--data-dir] [--data-dev]
                         [--journal-uuid UUID] [--journal-file]
                         [--journal-dev] [--bluestore] [--block-uuid UUID]
                         [--block-file] [--block-dev]
                         DATA [JOURNAL] [BLOCK]
...