[fanout connect playbook] Fix variable undefined in rootfanout_connect.yml (#16634)

Summary:
Fixes # (issue)
In PR: #15643, it add a new optional variable clean_before_add for template arista_7260_connect.j2 to indicate whether clean vlan range before add vlan range, however, this variable are defined in fanout_connect.yml which will call rootfanout_connect.yml, this will be a bug, because when rootfanout_connect.yml is called by other playbook, it will raise error: clean_before_add undefined, so, to fix this bug, we move the clean_before_add definition from fanout_connect.yml to
rootfanout_connect.yml.

What is the motivation for this PR?
this will be a bug, because when rootfanout_connect.yml is called by other playbook, it will raise error: clean_before_add undefined

How did you do it?
move the clean_before_add definition from fanout_connect.yml to
rootfanout_connect.yml.

How did you verify/test it?
local run playbook

Author: w1nda

ansible/fanout_connect.yml

@@ -11,7 +11,6 @@
         - set_fact:
             server: "{{ inventory_hostname|lower }}"
             server_port: "{{ external_port }}"
-            clean_before_add: "{{ clean_before_add | default('y') }}"
 
         - set_fact: root_fanout_connect=true
           when: root_fanout_connect is not defined

ansible/roles/fanout/tasks/rootfanout_connect.yml

@@ -7,6 +7,9 @@
 - set_fact: dut="{{ leaf_name }}"
   when: deploy_leaf
 
+- set_fact:
+    clean_before_add: "{{ clean_before_add | default('y') }}"
+
 - debug: msg="Configuring fanout switch for {{ dut }}"
 
 - name: Gathering connection facts about the DUTs or leaffanout device