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 <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/3d8cc701-df4e-f949-1715-5118b530e990@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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

@@ -13,7 +13,7 @@ skip_if_no_z_record() {
 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() {