Make sure rabbitmq_management.delegate_count is always set

Author: michaelklishin

deps/rabbitmq_management/BUILD.bazel

@@ -35,7 +35,8 @@ APP_ENV = """[
 	    {cors_allow_origins, []},
 	    {cors_max_age, 1800},
 	    {content_security_policy, "script-src 'self' 'unsafe-eval' 'unsafe-inline'; object-src 'self'"},
-	    {max_http_body_size, 10000000}
+	    {max_http_body_size, 10000000},
+        {delegate_count, 5}
 	  ]"""
 
 genrule(

deps/rabbitmq_management_agent/src/rabbit_mgmt_agent_sup.erl

@@ -58,5 +58,4 @@ maybe_enable_metrics_collector() ->
     end.
 
 get_management_delegate_count() ->
-    {ok, MDC} = application:get_env(rabbitmq_management, delegate_count),
-    MDC.
+    application:get_env(rabbitmq_management, delegate_count, 5).