perf tests: Show refcounting broken expectations in thread-mg-share test

perf tests: Show refcounting broken expectations in thread-mg-share test

To help understand the failure.

  [acme@zoo linux]$ perf test -v 30
  30: Test thread mg sharing                                 :
  --- start ---
  test child forked, pid 12275
  FAILED tests/thread-mg-share.c:68 wrong refcnt (4 != 3)
  test child finished with -1
  ---- end ----
  Test thread mg sharing: FAILED!
  [acme@zoo linux]$

This is under investigation, the thread__delete() calls were replaced
with thread__put(), and those cause mismatches because now we need to be
more judicious with the thread lifetime management.

I.e. previously the thread__delete() would drop the map_group refcount,
but now since thread__put doesn't call thread__delete() necessarily.
because we have other refcount holders, the map_group refcount will not
be as we expected when this test was implemented.

Will be fixed soon...

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-9y8e3f7ukzco5loxvnlitpfq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>