Cleanup and fixed issue with permanent redirect

src/Umbraco.Core/UriExtensions.cs

@@ -117,7 +117,7 @@ namespace Umbraco.Core
                                     .TrimStart("/");
 
             //check if this is in the umbraco back office
-            return afterAuthority.InvariantStartsWith(hostingEnvironment.ToAbsolute("~/install").TrimStart("/"));
+            return afterAuthority.InvariantStartsWith(hostingEnvironment.ToAbsolute(Constants.SystemDirectories.Install).TrimStart("/"));
         }
 
         /// <summary>

src/Umbraco.Web.Common/Extensions/UmbracoInstallApplicationBuilderExtensions.cs

@@ -50,9 +50,9 @@ namespace Umbraco.Extensions
                             var uri = context.Request.GetEncodedUrl();
                             // redirect to install
                             ReportRuntime(logger, runtime.Level, "Umbraco must install or upgrade.");
-                            
+
                             var installUrl = $"{installPath}?redir=true&url={uri}";
-                            context.Response.Redirect(installUrl, true);
+                            context.Response.Redirect(installUrl, false);
                             return Task.CompletedTask;
                         });