[Agent] fix optional plugin doesn't works
[Agent] fix optional plugin doesn't works

apache/skywalking,OpenSkywalking/skywalking,ascrutae/sky-walking,apache/skywalking,apache/skywalking,ascrutae/sky-walking,OpenSkywalking/skywalking,apache/skywalking,apache/skywalking,ascrutae/sky-walking,ascrutae/sky-walking,apache/skywalking,apache/skywalking,hanahmily/sky-walking,hanahmily/sky-walking