Fix GetComputerName xUnit test and repin monad

src/monad

@@ -1 +1 @@
-Subproject commit 44427ec1f38f443a8b90a48e50a4d40beed0fa05
+Subproject commit 8e014f44d72765f086fe516e870602d5a476076e

src/ps_test/test_CorePsPlatform.cs

@@ -71,7 +71,8 @@ namespace PSTests
         {
             var startInfo = new ProcessStartInfo
             {
-                FileName = @"/usr/hostname",
+                FileName = @"/usr/bin/env",
+                Arguments = "hostname",
                 RedirectStandardOutput = true,
                 UseShellExecute = false
             };