[conn_graph] Fix the fanout connection parsing error

[neethajohn]

Description of PR

Fanout graph parsing was broken due to #2517
Following errors were seen while running pfcwd tests
E RunAnsibleModuleFail: run module conn_graph_facts failed, Ansible Results =>
E {
E "changed": false,
E "failed": true,
E "invocation": {
E "module_args": {
E "anchor": null,
E "filename": "/var/nejo/Networking-acs-sonic-mgmt/tests/common/fixtures/../../../ansible/files/starlab_connection_graph.xml",
E "filepath": null,
E "host": "str-7260cx3-acs-fan-05",
E "hosts": null
E }
E },
E "msg": "Did not find port for Ethernet23/1 in the ports based on hwsku 'Arista-7260CX3' for host str-7260cx3-acs-fan-05"
E }

Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

How did you do it?

Parsing logic added in #2517 was for SONIC duts. Retained the old logic when dev type is FanoutLeaf

How did you verify/test it?

Ran one of the pfcwd tests and it passed

[lolyu]

LGTM, thanks!