perf tests: Fixes hang in zstd compression test by changing the source of random data

Running 'perf test' with zstd compression linked will hang at the test
'Zstd perf.data compression/decompression' because /dev/random blocks
reads until there is enough entropy. This means that the test will
appear to never complete unless the mouse is continually moved while
running it.

Signed-off-by: James Clark <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Alexey Budankov <[e-mail]>
Cc: Jeremy Linton <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

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

···
 collect_z_record() {
 	echo "Collecting compressed record file:"
 	$perf_tool record -o $trace_file -g -z -F 5000 -- \
-		dd count=500 if=/dev/random of=/dev/null
+		dd count=500 if=/dev/urandom of=/dev/null
 }
 
 check_compressed_stats() {