Avoid crash when reporting federation status (backport #13701) (backport #13708)

[mergify]

This should address crashes like this in (found in user's logs):

exception error: no case clause matching
                  [[{connection_details,[]},
                    {name,<<"10.0.13.41:50497 -> 10.2.230.128:5671 (1)">>},
                    {node,rabbit@foobar},
                    {number,1},
                    {user,<<"...">>},
                    {user_who_performed_action,<<"...">>},
                    {vhost,<<"/">>}],
                   [{connection_details,[]},
                    {name,<<"10.0.13.41:50142 -> 10.2.230.128:5671 (1)">>},
                    {node,rabbit@foobar},
                    {number,1},
                    {user,<<"...">>},
                    {user_who_performed_action,<<"...">>},
                    {vhost,<<"/">>}]]
   in function  rabbit_federation_mgmt:format/3 (rabbit_federation_mgmt.erl, line 100)
   in call from rabbit_federation_mgmt:'-status/3-lc$^0/1-0-'/4 (rabbit_federation_mgmt.erl, line 89)
   in call from rabbit_federation_mgmt:'-status/4-lc$^0/1-0-'/3 (rabbit_federation_mgmt.erl, line 82)
   in call from rabbit_federation_mgmt:'-status/4-lc$^0/1-0-'/3 (rabbit_federation_mgmt.erl, line 82)
   in call from rabbit_federation_mgmt:status/4 (rabbit_federation_mgmt.erl, line 82)
   in call from rabbit_federation_mgmt:to_json/2 (rabbit_federation_mgmt.erl, line 57)
   in call from cowboy_rest:call/3 (src/cowboy_rest.erl, line 1590)
   in call from cowboy_rest:set_resp_body/2 (src/cowboy_rest.erl, line 1473)
```<hr>This is an automatic backport of pull request #13701 done by [Mergify](https://mergify.com).<hr>This is an automatic backport of pull request #13708 done by [Mergify](https://mergify.com).