Fix start_test not suppressing timeout errors (#25200)

Fixes an issue were `start_test` would not suppress timeout errors
properly. Adjusted `sub_test` to add the appropriate future line.

[Review by @jeremiah-corrado]

util/test/sub_test.py

@@ -2481,7 +2481,7 @@ def run_compileline(flag, lookingfor):
                                 sys.stdout.write(']\n')
                         # only notify for a failed execution if launching the test was successful
                         elif (not launcher_error):
-                            sys.stdout.write('[Error execution failed for %s]\n'%(test_name))
+                            sys.stdout.write('%s[Error execution failed for %s]\n'%(futuretest,test_name))
 
                         if exectimeout or status != 0 or exec_status != 0:
                             break