TUI help states for multiple event sessions the TAB/UNTAB keys are used
to switch events. For single event sessions (e.g., the default) the tab
key currently causes the tui to exit. Change that to do nothing since
there is not no second event to switch to.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1319045867-12728-1-git-send-email-dsahern@gmail.comSigned-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>