perf trace: Don't supress zeroed args when there is an strarray entry for it

perf trace: Don't supress zeroed args when there is an strarray entry for it

Case in hand:

   9.682 ( 0.001 ms): Xorg/13079 setitimer(which: REAL, value: 0x7fffede42470) = 0

ITIMER_REAL is zero.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-6hnoqsjh99t4hxi3xu2nlwep@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>