perf top browser: Fix up exit keys

The left key was exiting 'perf top --tui' when it really shouldn't, it
was too easy to leave the live annotation window and then press one too
many <- and get out of the tool altogether.

Do just like the report TUI does, ignore the left key for exit and also
ask the user when pressing ESC if that is really what is wanted.

Reported-by: Mike Galbraith <efault@gmx.de>
Suggested-by: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>