fix(tar): use sync codepath on sync methods (#791)

Author: flensrocker

src/ICSharpCode.SharpZipLib/Tar/TarInputStream.cs

@@ -531,7 +531,7 @@ public void Reset()
 		/// <returns>
 		/// The next TarEntry in the archive, or null.
 		/// </returns>
-		public TarEntry GetNextEntry() => GetNextEntryAsync(CancellationToken.None, true).GetAwaiter().GetResult();
+		public TarEntry GetNextEntry() => GetNextEntryAsync(CancellationToken.None, false).GetAwaiter().GetResult();
 
 		private async ValueTask<TarEntry> GetNextEntryAsync(CancellationToken ct, bool isAsync)
 		{

src/ICSharpCode.SharpZipLib/Tar/TarOutputStream.cs

@@ -381,7 +381,7 @@ private async Task PutNextEntryAsync(TarEntry entry, CancellationToken cancellat
 		/// to the output stream before this entry is closed and the
 		/// next entry written.
 		/// </summary>
-		public void CloseEntry() => CloseEntryAsync(CancellationToken.None, true).GetAwaiter().GetResult();
+		public void CloseEntry() => CloseEntryAsync(CancellationToken.None, false).GetAwaiter().GetResult();
 
 		private async Task CloseEntryAsync(CancellationToken cancellationToken, bool isAsync)
 		{