Explicitly close release signal file. (#12057)

Author: Paul Johnson

src/Umbraco.Infrastructure/Runtime/FileSystemMainDomLock.cs

@@ -68,7 +68,8 @@ public Task<bool> AcquireLockAsync(int millisecondsTimeout)
         }
 
         public void CreateLockReleaseSignalFile() =>
-            _ = File.Open(_releaseSignalFilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete);
+            File.Open(_releaseSignalFilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete)
+                .Close();
 
         public void DeleteLockReleaseSignalFile() =>
             File.Delete(_releaseSignalFilePath);

tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Runtime/FileSystemMainDomLockTests.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
@@ -44,13 +45,23 @@ public void SetUp()
         [TearDown]
         public void TearDown()
         {
-            while (File.Exists(LockFilePath))
-            {
-                File.Delete(LockFilePath);
-            }
-            while (File.Exists(LockReleaseFilePath))
+            CleanupTestFile(LockFilePath);
+            CleanupTestFile(LockReleaseFilePath);
+        }
+
+        private static void CleanupTestFile(string path)
+        {
+            for (var i = 0; i < 3; i++)
             {
-                File.Delete(LockReleaseFilePath);
+                try
+                {
+                    File.Delete(path);
+                    return;
+                }
+                catch
+                {
+                    Thread.Sleep(500 * (i + 1));
+                }
             }
         }