Add incompatibility info for "ip floating list" command

Commit d8abec3 changed
the output of "ip floating list" command. But forgot to
add any backward incompatibility info.

Output of command "ip floating list" for nova network
has been changed. And it is different from the output
of neutron network.

This patch adds this incompatibility info.

Change-Id: I45858fda3b9bcc0bdf4d0891637fa7dd712872af
Partial-Bug: 1519502
Related-to: blueprint neutron-client

Author: Tang Chen

doc/source/backwards-incompatible.rst

@@ -162,6 +162,36 @@ List of Backwards Incompatible Changes
   * Bug: https://bugs.launchpad.net/python-openstackclient/+bug/1546065
   * Commit: https://review.openstack.org/#/c/281089/
 
+14. Output of `ip floating list` command has changed.
+
+  When using Compute v2, the original output of `ip floating list` command is:
+  +----+--------+------------+----------+-------------+
+  | ID | Pool   | IP         | Fixed IP | Instance ID |
+  +----+--------+-----------------------+-------------+
+  |  1 | public | 172.24.4.1 | None     | None        |
+  +----+--------+------------+----------+-------------+
+
+  Now it changes to:
+  +----+---------------------+------------------+-----------+--------+
+  | ID | Floating IP Address | Fixed IP Address | Server ID | Pool   |
+  +----+---------------------+------------------+-----------+--------+
+  |  1 | 172.24.4.1          | None             | None      | public |
+  +----+---------------------+------------------+-----------+--------+
+
+  When using Network v2, the output of `ip floating list` command is:
+  +--------------------------------------+---------------------+------------------+------+
+  | ID                                   | Floating IP Address | Fixed IP Address | Port |
+  +--------------------------------------+---------------------+------------------+------+
+  | 1976df86-e66a-4f96-81bd-c6ffee6407f1 | 172.24.4.3          | None             | None |
+  +--------------------------------------+---------------------+------------------+------+
+  which is different from Compute v2.
+
+  * In favor of: Use `ip floating list` command
+  * As of: NA
+  * Removed in: NA
+  * Bug: https://bugs.launchpad.net/python-openstackclient/+bug/1519502
+  * Commit: https://review.openstack.org/#/c/277720/
+
 For Developers
 ==============
 

releasenotes/notes/bug-1519502-f72236598d14d350.yaml

@@ -6,3 +6,7 @@ features:
     [Bug `1519502 <https://bugs.launchpad.net/python-openstackclient/+bug/1519502>`_]
   - Add command ``ip floating show`` for neutron and nova network.
     [Bug `1519502 <https://bugs.launchpad.net/python-openstackclient/+bug/1519502>`_]
+upgrade:
+  - Output of command ``ip floating list`` for nova network has been changed.
+    And it is different from the output of neutron network.
+    [Ref `<http://docs.openstack.org/developer/python-openstackclient/backwards-incompatible.html>`_]