MINOR: server/event_hdl: add proxy_uuid to event_hdl_cb_data_server

Expose proxy_uuid variable in event_hdl_cb_data_server struct to
overcome proxy_name fixed length limitation.

proxy_uuid may be used by the handler to perform proxy lookups.
This should be preferred over lookups relying proxy_name.
(proxy_name is suitable for printing / logging purposes but not for
ID lookups since it has a maximum fixed length)
diff --git a/src/server.c b/src/server.c
index 1247537..d17436c 100644
--- a/src/server.c
+++ b/src/server.c
@@ -151,8 +151,12 @@
 	cb_data.safe.rid = srv->rid;
 	cb_data.safe.flags = srv->flags;
 	snprintf(cb_data.safe.name, sizeof(cb_data.safe.name), "%s", srv->id);
-	if (srv->proxy)
+	cb_data.safe.proxy_name[0] = '\0';
+	cb_data.safe.proxy_uuid = -1; /* default value */
+	if (srv->proxy) {
+		cb_data.safe.proxy_uuid = srv->proxy->uuid;
 		snprintf(cb_data.safe.proxy_name, sizeof(cb_data.safe.proxy_name), "%s", srv->proxy->id);
+	}
 	/* unsafe data assignments */
 	cb_data.unsafe.ptr = srv;
 	cb_data.unsafe.thread_isolate = thread_isolate;