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 <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Disha Goel <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kajol Jain <[e-mail]>
Cc: Madhavan Srinivasan <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Nageswara R Sastry <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: [e-mail]
Link: http://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/record+probe_libc_inet_pton.sh

···
 	perf_data=`mktemp -u /tmp/perf.data.XXX`
 	perf_script=`mktemp -u /tmp/perf.script.XXX`
 	perf record -e $event_name/$eventattr/ -o $perf_data ping -6 -c 1 ::1 > /dev/null 2>&1
+	# check if perf data file got created in above step.
+	if [ ! -e $perf_data ]; then
+		printf "FAIL: perf record failed to create \"%s\" \n" "$perf_data"
+		return 1
+	fi
 	perf script -i $perf_data | tac | grep -m1 ^ping -B9 | tac > $perf_script
 
 	exec 3<$perf_script