Changed IsDocker check (#1998)

* Refactored IsDocker to be completely static and changed to use an environment variable instead.

* Removed file from another branch

API/Services/Tasks/StatsService.cs

@@ -119,7 +119,7 @@ public class StatsService : IStatsService
             Os = RuntimeInformation.OSDescription,
             KavitaVersion = serverSettings.InstallVersion,
             DotnetVersion = Environment.Version.ToString(),
-            IsDocker = new OsInfo().IsDocker,
+            IsDocker = OsInfo.IsDocker,
             NumOfCores = Math.Max(Environment.ProcessorCount, 1),
             UsersWithEmulateComicBook = await _context.AppUserPreferences.CountAsync(p => p.EmulateBook),
             TotalReadingHours = await _statisticService.TimeSpentReadingForUsersAsync(ArraySegment<int>.Empty, ArraySegment<int>.Empty),

API/Services/Tasks/VersionUpdaterService.cs

@@ -100,7 +100,7 @@ public class VersionUpdaterService : IVersionUpdaterService
             UpdateBody = _markdown.Transform(update.Body.Trim()),
             UpdateTitle = update.Name,
             UpdateUrl = update.Html_Url,
-            IsDocker = new OsInfo(Array.Empty<IOsVersionAdapter>()).IsDocker,
+            IsDocker = OsInfo.IsDocker,
             PublishDate = update.Published_At
         };
     }