#263 Disable parallel test execution to improve reliability

test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Properties/AssemblyInfo.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNetCore.Testing.xunit;
+using Xunit;
 
 [assembly: OSSkipCondition(OperatingSystems.MacOSX)]
-[assembly: OSSkipCondition(OperatingSystems.Linux)]
+[assembly: OSSkipCondition(OperatingSystems.Linux)]
+[assembly: CollectionBehavior(DisableTestParallelization = true)]