perf test stat tests: Fix for virtualized machines

perf test stat tests: Fix for virtualized machines

On s390 'perf test's 'perf stat tests', subtest test_hybrid fails for
z/VM systems.  The root cause is this statement:

  $(perf stat -a -- sleep 0.1 2>&1 |\
                  grep -E "/cpu-cycles/[uH]*|  cpu-cycles[:uH]* -c)

The 'perf stat' output on a s390 z/VM system is

  # perf stat -a -- sleep 0.1 2>&1
  Performance counter stats for 'system wide':

        56      context-switches  #     46.3 cs/sec  cs_per_second
  1,210.41 msec cpu-clock         #     11.9 CPUs  CPUs_utilized
        12      cpu-migrations    #      9.9 migrations/sec ...
        81      page-faults       #     66.9 faults/sec ...

        0.100891009 seconds time elapsed

The grep command does not match any single line and exits with error
code 1.

As the bash script is executed with 'set -e', it aborts with the first
error code being non-zero.

Fix this and use 'wc -l' to count matching lines instead of 'grep ... -c'.

Output before:

  # perf test 102
  102: perf stat tests                      : FAILED!
  #

Output after:

  # perf test 102
  102: perf stat tests                      : Ok
  #

Fixes: bb6e7cb11d97ce19 ("perf tools: Add fallback for exclude_guest")
Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Jan Polensky <japo@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>