perf test: Remove leftover temp file left by one of the attr tests

Instead of > /tmp/krava, direct it to /dev/null.

Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/attr/test-record-group1

···
 [config]
 command = record
-args    = -e '{cycles,instructions}' kill >/tmp/krava 2>&1
+args    = -e '{cycles,instructions}' kill >/dev/null 2>&1
 
 [event-1:base-record]
 fd=1