Removing has_group_leader_pid

With de_thread now calling exchange_tids has_group_leader_pid no longer
makes any sense and is equivalent to calling thread_group_leader.

As there are only 2 remaining users of has_group_leader_pid let's
update the code and get rid of has_group_leader_pid.

There is one extra patch to lookup_task that performs that unifies
to code paths that become identical when has_group_leader_pid went
away.

Eric W. Biederman (4):
      posix-cpu-timer: Tidy up group_leader logic in lookup_task
      posix-cpu-timer:  Unify the now redundant code in lookup_task
      exec: Remove BUG_ON(has_group_leader_pid)
      signal: Remove has_group_leader_pid

 fs/exec.c                      |  1 -
 include/linux/sched/signal.h   | 11 -----------
 kernel/time/posix-cpu-timers.c | 21 ++++++++-------------
 3 files changed, 8 insertions(+), 25 deletions(-)

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>