[ansible][minigraph] Fix minigraph template for devices which have autoneg enabled but the topo file does not contain autoneg interfaces (#15134)

This pull request updates the Jinja2 template minigraph_link_meta.j2 by modifying the generation of the section.

Key Changes:
* The condition has been changed from simply checking if msft_an_enabled is defined to also checking if vm_topo_config.get('autoneg_interfaces') is not None.
* This ensures that the section is only included if both msft_an_enabled is defined and the autoneg_interfaces attribute in vm_topo_config exists and is not None.

This ensures if some testbeds/devices have msft_an_enabled they do not end up treated as autoneg devices unless the topo file contains the AN interface list

Signed-off-by: Vaibhav Dahiya <vdahiya@microsoft.com>

Author: vdahiya12

ansible/templates/minigraph_link_meta.j2

@@ -53,7 +53,7 @@
   </LinkMetadataDeclaration>
 {% endif %}
 
-{% if msft_an_enabled is defined %}
+{% if msft_an_enabled is defined and vm_topo_config.get('autoneg_interfaces') is not none %}
   <LinkMetadataDeclaration>
     <Link xmlns:a="http://schemas.datacontract.org/2004/07/Microsoft.Search.Autopilot.Evolution">
 {% for if_index in vm_topo_config['autoneg_interfaces']['intfs'] %}