plug: fix SEGV of elementary_test during reconnecting

Summary:
problem:
1. open window socket
2. open window plug
3. close window socket
4. open window socket
5. SEGV

there was invalid timer deletion due to dangling pointer.

@fix

Test Plan: elementary_test -> open window socket -> open window plug -> close window socket -> open window socket ->SEGV

Reviewers: raster, seoz

Reviewed By: raster

CC: seoz

Differential Revision: https://phab.enlightenment.org/D699

legacy/elementary/src/bin/test_win_plug.c

@@ -35,6 +35,7 @@ cb_plug_connect(void *data)
    if (elm_plug_connect(obj, "ello", 0, EINA_FALSE))
      {
         printf("plug connect to server[ello]\n");
+        evas_object_data_del(obj, "test-timer");
         return ECORE_CALLBACK_CANCEL;
      }