Don't lose the stack when rethrowing exceptions from TestHost (#1060)

src/testhost.x86/Program.cs

@@ -39,7 +39,7 @@ public static void Main(string[] args)
                 EqtTrace.Error("TestHost: Error occured during initialization of TestHost : {0}", ex);
 
                 // Throw exception so that vstest.console get the exception message.
-                throw ex;
+                throw;
             }
             finally
             {