Fix pdu issue (#20405)

The secret_group_vars is not always exist for all users, need to allow
the secret_group_vars not defined as previously, the logic was broke by
the PR: #20269

Signed-off-by: selldinesh <dinesh.sellappan@keysight.com>

Author: nhe-NV

tests/common/plugins/pdu_controller/snmp_pdu_controllers.py

@@ -215,7 +215,9 @@ def _render_value(self, value, context):
         return value
 
     def _get_pdu_snmp_creds(self, pdu, perm):
-        context = {'secret_group_vars': pdu['secret_group_vars']}
+        context = {}
+        if 'secret_group_vars' in pdu:
+            context = {'secret_group_vars': pdu['secret_group_vars']}
         if 'pdu_{}_snmp_version'.format(perm) in pdu:
             version = pdu['pdu_{}_snmp_version'.format(perm)]
             if version == 'v2c':