perf list: Avoid confusion of perf output and the next command prompt

Distinguish the output of 'perf list --list-opts' or 'perf --list-cmds'
with the next command prompt, which also happens in other cases (e.g.
record, report ...).

Example:

Before this patch:

 $perf list --list-opts
 --raw-dump $          <-- the output and the next command prompt are at
                           the same line

After this patch:

 $perf list --list-opts
 --raw-dump
 $                     <-- the new line

Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1425032491-20224-6-git-send-email-yunlong.song@huawei.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>