Description of problem:
======================
While verifying bug 1459839, noticed that gluster-block create help has no mention of newly added "prealloc <full|no>" option. 

[root@dhcp47-121 ~]# gluster-block create
Inadequate arguments for create:
gluster-block create <volname/blockname> [ha <count>] [auth enable|disable] <HOST1[,HOST2,...]> <size> [--json*]
[root@dhcp47-121 ~]# 

"gluster-block help" does list it under the create section though. It seems to have gotten missed adding the same in "gluster-block create help"

Though a minor change, I would consider this important if we are exposing the gluster-block CLI to the user. If not, we could choose to live with it .. as the api calls in CNS environment are not going to be affected with this.


Version-Release number of selected component (if applicable):
=============================================================
glusterfs-3.8.4-31, gluster-block-0.2.1-3


How reproducible:
=================
Always

Additional info:
==================

[root@dhcp47-121 ~]# gluster-block 
gluster-block (0.2.1)
usage:
  gluster-block <command> <volname[/blockname]> [<args>] [--json*]

commands:
  create  <volname/blockname> [ha <count>]
                              [auth <enable|disable>]
                              [prealloc <full|no>]
                              <host1[,host2,...]> <size>
        create block device [defaults: ha 1, auth disable, prealloc no]

  list    <volname>
        list available block devices.

  info    <volname/blockname>
        details about block device.

  delete  <volname/blockname>
        delete block device.

  modify  <volname/blockname> <auth enable|disable>
        modify block device.

  help
        show this message and exit.

  version
        show version info and exit.

supported JSON formats:
  --json|--json-plain|--json-spaced|--json-pretty
unknown option: (null)
[root@dhcp47-121 ~]#