plugin_proxy: change proxydef initialization to use calloc instead of malloc

Changing intialization to use calloc instead of malloc so that emtpy fields are 0 initialized.
Specifically for the event_type addition.

Signed-off-by: jmccormick7 <jcm258@case.edu>

Author: jmccormick7

src/flb_plugin_proxy.c

@@ -621,7 +621,7 @@ struct flb_plugin_proxy *flb_plugin_proxy_create(const char *dso_path, int type,
         return NULL;
     }
 
-    proxy->def = flb_malloc(sizeof(struct flb_plugin_proxy_def));
+    proxy->def = flb_calloc(1, sizeof(struct flb_plugin_proxy_def));
     if (!proxy->def) {
         flb_errno();
         dlclose(handle);