perf hists browser: Check sort keys before hot key actions

The context menu in TUI hists browser checks corresponding sort keys
when creating the menu item.  But hotkey actions lacks these checks so
it can filter using incorrect info.

For example, default sort key of 'perf top' doesn't contain 'comm' or
'pid' sort key so each hist entry's thread info is not reliable.  Thus
it should prohibit using thread filter on 't' key.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1457533253-21419-3-git-send-email-namhyung@kernel.org


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