Merge commits 'ca6a42586fae' and 'c286c419c784' into perf/urgent

Pick up these two commits from Arnaldo's perf/core tree:

  ca6a42586fae: perf tools: Emit clearer message for sys_perf_event_open ENOENT return
  c286c419c784: perf tools: Fixup exit path when not able to open events

As they are really fixes we want to have sooner than laer.

Signed-off-by: Ingo Molnar <[email protected]>