perf hists browser: Fix TAB/UNTAB use with multiple events

When requesting multiple events, say:

  # perf top -e instructions -e cycles -e cache-misses

The first screen lets the user chose what to see first, then to switch
one can either use the left key to get back to the event menu or simply
use TAB to go the next and shift+TAB to go the prev.

When using TAB/UNTAB the call to perf_evlist__set_selected(event) was
missing, fix it.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-3xqqh3fwmt914gg43frey14y@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>