perf hists browser: Skip scripting when perf.data file not available

The script and data-switch context menu are only meaningful when it
deals with a data file.  So add a check so that it cannot be shown when
perf-top is run.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1453555902-18401-4-git-send-email-namhyung@kernel.org


[ Use goto skip_scripting instead of two is_report_browser() tests ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>