fix: Include config file path in the "Agent is disabled " message on all platforms. (#1727)

Author: tippmar-nr

src/Agent/NewRelic/Agent/Core/Config/ConfigurationLoader.cs

@@ -111,6 +111,14 @@ public static ValueWithProvenance<string> GetConfigSetting(string key)
 				value = new ValueWithProvenance<string>(ConfigurationManager.AppSettings[key],
 					"ConfigurationManager app setting");
 			}
+#else
+            if (value?.Value == null)
+            {
+                var configMgrStatic = new ConfigurationManagerStatic();
+                var configValue = configMgrStatic.GetAppSetting(key);
+                if (configValue != null)
+                    value = new ValueWithProvenance<string>(configValue, configMgrStatic.AppSettingsFilePath);
+            }
 #endif
             return value;
         }

src/Agent/NewRelic/Agent/Core/NewRelic.Agent.Core/AgentManager.cs

@@ -152,7 +152,7 @@ private AgentManager()
         private void AssertAgentEnabled(configuration config)
         {
             if (!Configuration.AgentEnabled)
-                throw new Exception(string.Format("The New Relic agent is disabled.  Update {0}  to re-enable it.", config.AgentEnabledAt));
+                throw new Exception(string.Format("The New Relic agent is disabled.  Update {0}  to re-enable it.", config.AgentEnabledAt ?? config.ConfigurationFileName));
 
             if ("REPLACE_WITH_LICENSE_KEY".Equals(Configuration.AgentLicenseKey))
                 throw new Exception("Please set your license key.");