add bandwidth test conf

+# bandwidth test tool config for srs.
+# @see full.conf for detail config.
+
+listen              1935;
+vhost __defaultVhost__ {
+}
+
+vhost bandcheck.srs.com {
+    enabled         on;
+    chunk_size      65000;
+    bandcheck {
+        enabled         on;
+        key             "35c9b402c12a7246868752e2878f7e0e";
+        interval        30;
+        limit_kbps      4000;
+    }
+}