fixed parameter

jenkins/default_backup.yml

@@ -7,7 +7,7 @@ pipeline {
         string(name: 'agentname', defaultValue: params.directory ?: 'any', description: 'The agent to run this backup on')
         text(name: 'excludelist', defaultValue:  params.excludelist ?: '**/cache/** ', description: 'Multiline string to exclude patterns from backup')
     }
-    agent params.agentname
+    agent { label "${params.agentname}" }
     environment {
         BORG_RELOCATED_REPO_ACCESS_IS_OK = 'yes'
     }