Improve logic around decide IsHostedServer. (#4086)

src/Runner.Common/ConfigurationStore.cs

@@ -1,10 +1,10 @@
-using GitHub.Runner.Sdk;
+using System;
-using System;
 using System.IO;
 using System.Linq;
 using System.Runtime.Serialization;
 using System.Text;
 using System.Threading;
+using GitHub.Runner.Sdk;
 
 namespace GitHub.Runner.Common
 {
@@ -64,8 +64,20 @@ namespace GitHub.Runner.Common
         {
             get
             {
-                // Old runners do not have this property. Hosted runners likely don't have this property either.
+                // If the value has been explicitly set, return it.
-                return _isHostedServer ?? true;
+                if (_isHostedServer.HasValue)
+                {
+                    return _isHostedServer.Value;
+                }
+
+                // Otherwise, try to infer it from the GitHubUrl.
+                if (!string.IsNullOrEmpty(GitHubUrl))
+                {
+                    return UrlUtil.IsHostedServer(new UriBuilder(GitHubUrl));
+                }
+
+                // Default to true since Hosted runners likely don't have this property set.
+                return true;
             }
 
             set