perf test: Fix subtest number when showing results

perf test: Fix subtest number when showing results

Perf test 40 for example has several subtests numbered 1-4 when
displaying the start of the subtest. When the subtest results
are displayed the subtests are numbered 0-3.

Use this command to generate trace output:

  [root@s35lp76 perf]# ./perf test -Fv 40 2>/tmp/bpf1

Fix this by adjusting the subtest number when show the
subtest result.

Output before:

  [root@s35lp76 perf]# egrep '(^40\.[0-4]| subtest [0-4]:)' /tmp/bpf1
  40.1: Basic BPF filtering                                 :
  BPF filter subtest 0: Ok
  40.2: BPF pinning                                         :
  BPF filter subtest 1: Ok
  40.3: BPF prologue generation                             :
  BPF filter subtest 2: Ok
  40.4: BPF relocation checker                              :
  BPF filter subtest 3: Ok
  [root@s35lp76 perf]#

Output after:

  root@s35lp76 ~]# egrep '(^40\.[0-4]| subtest [0-4]:)' /tmp/bpf1
  40.1: Basic BPF filtering                                 :
  BPF filter subtest 1: Ok
  40.2: BPF pinning                                         :
  BPF filter subtest 2: Ok
  40.3: BPF prologue generation                             :
  BPF filter subtest 3: Ok
  40.4: BPF relocation checker                              :
  BPF filter subtest 4: Ok
  [root@s35lp76 ~]#

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Link: http://lkml.kernel.org/r/20180724134858.100644-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>