fix temporary file name to have subtest number

(cherry picked from commit e12453f4)
7 jobs for fixfilename in 7 minutes and 58 seconds (queued for 38 seconds)
Status Job ID Name Coverage
  Precheck
passed #5343
linux docker
precheck:debian:sid:amd64

00:00:11

 
  Build
passed #5344
linux docker
build:debian:sid:amd64

00:02:29

passed #5345
linux docker
build:debian:sid:i386

00:02:41

 
  Test
passed #5348
linux docker
systemtest:debian:sid:amd64

00:04:49

passed #5349
linux docker
systemtest:debian:sid:i386

00:04:55

passed #5346
linux docker
unittest:debian:sid:amd64

00:00:50

passed #5347
linux docker
unittest:debian:sid:i386

00:00:50