vpp: fix stdin vs non-interactive command clash
In case of both stdin and non-interactive inputs are there
vppctl parses them all, causing mixed corrupted output:
$ echo foo | vppctl sh bar
show: unknown input `bar'
unknown input `foo'
This is not desired, stdin should be ignored if there's a command
but still allow stdin commands - following cases are still equal:
$ vppctl foo
$ echo foo | vppctl
Type: fix
Signed-off-by: Vladislav Grishenko <themiron@yandex-team.ru>
Change-Id: I98667391627150c98a57d49ae544e48ef3351f34