Update pre_requisites.yml

Signed-off-by: sakshiarora13 <sakshi_arora1@dell.com>

control_plane/roles/network_ethernet/tasks/pre_requisites.yml

@@ -16,6 +16,7 @@
 - name: Install paramiko
   command: pip3 install paramiko -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com
   delegate_to: localhost
+  run_once: true
   changed_when: false
 
 - name: Check if ethernet_tor_vars.yml exists
@@ -71,4 +72,4 @@
         success_msg: "{{ success_msg_save_config }}"
         fail_msg: "{{ fail_msg_save_config }}"
 
-  when: "'S3' not in model_type and 'S4' not in model_type"
+  when: "'S3' not in model_type and 'S4' not in model_type"