perf sched latency: Fix thread pid reuse issue

perf sched latency: Fix thread pid reuse issue

The latency subcommand holds a tree of working atoms sorted by thread's
pid/tid. If there's new thread with same pid and tid, the old working atom is
found and assert bug condition is hit in search function:

  thread_atoms_search: Assertion `!(thread != atoms->thread)' failed

Changing the sort function to use thread object pointers together with pid and
tid check. This way new thread will never find old one with same pid/tid.

Link: http://lkml.kernel.org/n/tip-o4doazhhv0zax5zshkg8hnys@git.kernel.org
Reported-by: Mohit Agrawal <moagrawa@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1446462625-15807-1-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>