Fix 5646 junos_config issue if config format is text (#5658)

If 'src_format' is not mentioned in playbook
and config is in text format a list object is
passed to 'guess_format' function instead
of string, hence TypeError execption is seen.
Fix is to pass string object instead of list.

lib/ansible/modules/network/junos/junos_config.py

@@ -245,7 +245,7 @@ def load_config(module, result):
     kwargs['commit'] = not module.check_mode
 
     if module.params['src']:
-        config_format = module.params['src_format'] or guess_format(candidate)
+        config_format = module.params['src_format'] or guess_format(str(candidate))
     elif module.params['lines']:
         config_format = 'set'
     kwargs['config_format'] = config_format