add newline if the output formatter is json

[shizhihui]

When we use the command with output formatter is json, we may get result like these:

(1)
[root@zhihui cliff]# openstack volume type list -f json
[
  {
    "ID": "0a42e6d8-30a9-4281-892a-5e88d938a5ab",
    "Name": "lvmdriver-1"
  }
][root@zhihui cliff]#

(2)
[root@zhihui cliff]# openstack stack list -f json
[
  {
    "Updated Time": null,
    "Stack Status": "CREATE_COMPLETE",
    "Stack Name": "test",
    "ID": "ba94a8bd-7172-4ece-9294-66bfe763136b",
    "Creation Time": "2016-11-11T10:49:24Z"
  }
][root@zhihui cliff]#
...

The result is so terrible, so I fix it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/422488

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/422488
Committed: https://git.openstack.org/cgit/openstack/cliff/commit/?id=49ce4c18afc06a7b1766e5599d2f77f4a27e7b6e
Submitter: Jenkins
Branch: master

commit 49ce4c18afc06a7b1766e5599d2f77f4a27e7b6e
Author: shizhihui <email address hidden>
Date: Tue Nov 15 05:58:36 2016 +0800

    Add newline if the output formatter is json

    Change-Id: I4955a148713a9338b6c423e712576adcfd2305f1
    Closes-Bug: #1657683

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cliff 2.5.0 release.