perf tests shell: Add check for perf data file in record+probe_libc_inet_pton test

The "probe libc's inet_pton & backtrace it with ping" test installs a
uprobe and uses perf record/script to check the backtrace. Currently
even if the "perf record" fails, the test reports success. Logs below:

  # ./perf test -v "probe libc's inet_pton & backtrace it with ping"
  81: probe libc's inet_pton & backtrace it with ping                 :
  --- start ---
  test child forked, pid 304211
  failed to open /tmp/perf.data.Btf: No such file or directory
  test child finished with 0
  ---- end ----
  probe libc's inet_pton & backtrace it with ping: Ok

Fix this by adding check for presence of perf.data file
before proceeding with "perf script".

With the patch changes, test reports fail correctly.

 # ./perf test -v "probe libc's inet_pton & backtrace it with ping"
 81: probe libc's inet_pton & backtrace it with ping                 :
  --- start ---
  test child forked, pid 304358
  FAIL: perf record failed to create "/tmp/perf.data.Uoi"
  test child finished with -1
  ---- end ----
  probe libc's inet_pton & backtrace it with ping: FAILED!

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Disha Goel <disgoel@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nageswara R Sastry <rnsastry@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lore.kernel.org/r/20230201180421.59640-1-atrajeev@linux.vnet.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>